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When advised that I had been proposed to receive the Institute’s Hothersall Memorial Award and invited to present the Hothersall Memorial Lecture at the 2016 AGM my thought was what would be my the...

Flip-chip heterogeneously integrated n-p-n InGaP/GaAs heterojunction bipolar transistors (HBTs) with integrated thermal management on wide-bandgap AlN substrates followed by GaAs substrate removal are demonstrated. Without thermal management, substrate removal after integration significantly aggravates self-heating effects, causing poor $I$ – $V$ characteristics due to excessive device self-heating. An electrothermal codesign scheme is demonstrated that involves simulation (design), thermal characterization, fabrication, and evaluation. Thermoreflectance thermal imaging, electrical-temperature sensitive parameter-based thermometry, and infrared thermography were utilized to assess the junction temperature rise in HBTs under diverse configurations. In order to reduce the thermal resistance of integrated devices, passive cooling schemes assisted by structural modification, i.e., positioning indium bump heat sinks between the devices and the carrier, were employed. By implementing thermal heat sinks in close proximity to the active region of flip-chip integrated HBTs, the junction-to-baseplate thermal resistance was reduced over a factor of two, as revealed by junction temperature measurements and improvement of electrical performance. The suggested heterogeneous integration method accounts for not only electrical but also thermal requirements providing insight into realization of advanced and robust III-V/Si heterogeneously integrated electronics.

Step-stress experiments on high-voltage Npn InGaP/GaAs HBTs are shown to reveal a number of degradation mechanisms, singly or in combinations: defect buildup in the emitter depletion region, defect buildup in the neutral base region, possible degradation of Ohmic contacts or increase in epitaxial layer resistances. Defect buildup in the emitter depletion region often precedes other types of degradation. Two less commonly reported degradation mechanisms are also suggested: base Ohmic metal punch-through to the collector and deterioration of the die attach material. It was found that the vast majority of devices failed within 5% of a maximum attainable power level, but when stressed just shy of this catastrophic level, electrical characteristics typically degraded gradually.

Beta titanium alloys have been available since the 1950s (Ti-13V-11Cr-3Mo or B120VCA), but significant applications of these alloys, beyond the SR-71 Blackbird, have been slow in coming. The next significant usage of a β alloy did not occur until the mid-1980s on the B-1B bomber. This aircraft used Ti-15V-3Cr-3Al-3Sn sheet due to its capability for strip rolling, improved formability, and higher strength than Ti-6Al-4V. The next major usage was on a commercial aircraft, the Boeing 777, which made extensive use of Ti-10V-2Fe-3Al high-strength forgings. Ti-15V-3Cr-3Al-3Sn environmental control system ducting, castings, and springs were also used, along with Ti-3Al-8V-6Cr-4Mo-4Zr (β-C) springs. Beta-21S was also introduced for high-temperature usage. More recent work at Boeing has focused on the development of Ti-5Al-5Mo-5V-3Cr, a high-strength alloy that can be used at higher strength than Ti-10V-2Fe-3Al and is much more robust; it has a much wider, or friendlier, processing window. This, along with additional studies at Boeing, and from within the aerospace industry in general will be discussed in detail, summarizing applications and the rationale for the selection of this alloy system for aerospace applications.

The thermal stability of Au/Ti/WSi x contacts on 4H-SiC was examined by Auger electron spectroscopy and current–voltage measurements. The silicide-based contacts on SiC are found to exhibit improved thermal stability compared to pure W contacts. The Au/Ti/WSi x contacts show a maximum Schottky barrier height of ∼1.15 eV as obtained from current–voltage ( I – V ) measurements. After 500 °C anneals, the Ti diffuses to the surface of the contact structure, followed by a Au-rich layer and finally the WSi x . After 1000 °C anneals, the Ti and Au showed significant mixing. Particulates formed on the surface in the latter case were Au-rich phases.

Al0.2Ga0.8N/GaN HEMTs have been fabricated from MOCVD-grown epilayers on (0 0 0 1) sapphire substrates. DC current densities from 0.5 to ∼1 A/mm were achieved for gate lengths ranging from 0.75 to 0.1 μ m. A maximum transconductance of 207 mS/mm was measured for short gate length devices. From s-parameter measurements, ft of 59 GHz and fmax of 90 GHz were extracted. Load pull results from 0.25×150 μm 2 gate dimension devices indicated an output power density of 2.75 W/mm at 3 GHz and 1.7 W/mm at 10 GHz. Small signal modeling of the measured s-parameters is also presented.

Emitter orientation effects in AlGaAs/GaAs heterojunction bipolar transistors (HBTs) in which DC current gain was greater for the [0 1 1] emitter orientation compared to the [0 1 1 ] orientation were previously attributed to the piezoelectric effect, however no effects of dielectric overlayers were examined. In this work, we establish that for InGaP/GaAs HBTs, dielectric passivation effects can be as important as the piezoelectric effect. Non-self-aligned InGaP/GaAs HBTs with ECR SiON dielectric deposited at 25 °C exhibited greater stress and showed less current gain difference and lower base current ideality factors for these orientations than identical HBTs that were passivated with plasma enhanced chemical vapor deposition (PECVD) SiN dielectric. Non-self-aligned HBTs with ECR SiON passivation also showed slightly better rf performance for the [0 1 1] orientation with ft of 48 GHz compared to ft of 44 GHz for the [0 1 1 ] orientation. These differences in dielectrics are attributed to higher dielectric-induced damage in emitter–base space-charge region for the PECVD SiN film.

The temperature and gate length effects on dc performance of AlGaN/GaN high-electron mobility transistors (HEMTs) grown on AlN/SiC templates or sapphire substrates are reported. The defect density in the structures grown on the AlN/SiC template is significantly lower than those grown on sapphire, as measured by transmission electron microscopy. Reverse breakdown voltages above 40 V were obtained for 0.25 μm gate length devices on both types of substrate. Extrinsic transconductances of ∼200 mS/mm for HEMTs on sapphire and ∼125 mS/mm for devices on AlN/SiC were achieved, with the latter devices showing significantly lower self-heating effects. Both types of HEMTs showed similar trends of drain current and transconductance with increasing temperature. There was a clear signature of optical phonon scattering as the dominant scattering mechanism from room temperature to 300 °C.

The DC performance of AlGaN/GaN high electron mobility transistors grown by plasma-assisted molecular beam epitaxy was investigated for gate lengths in the range 0.1–1.2 μm. On 0.25 μm gate length devices we obtained 40 V DS operation with >50 mA peak I D . The peak drain current density was 0.44 A/mm for 100 μm gate width devices with 1.2 μm gate lengths. The extrinsic transconductance ( g m ) decreased with both gate length and gate width and was ⩾75 mS/mm for all gate widths for 0.25 μm devices. E-beam written gates typically produced a slightly lower Schottky barrier height than optically patterned gates.

A survey of ohmic contact materials and properties to GaAs, InP, GaN will be presented along with critical issues pertaining to each semiconductor material. Au-based alloys (e.g., GeAuNi for n-type GaAs) are the most commonly used contacts for GaAs and InP materials for both n- and p-type contacts due to the excellent contact resistivity, reliability, and usefulness over a wide range of doping levels. Research into new contacting schemes for these materials has focused on addressing limitations of the conventional Au-alloys in thermal stability, propensity for spiking, poor edge definition, and new approaches for a non-alloyed contact. The alternative contacts to GaAs and InP include alloys with higher temperature stability, contacts based on solid phase regrowth, and contacts that react with the substrate to form lower bandgap semiconductors alloys at the interface. A new area of contact studies is for the wide bandgap group III-Nitride materials. At present, low resistivity ohmic contact to p-type GaN has not been obtained primarily due to the large acceptor ionization energy and the resultant difficulty in achieving high free hole concentrations at room temperature. For n-type GaN, however, significant progress has been reported with reactive Ti-based metalization schemes or the use of graded InGaN layers. The present status of these approaches will be reviewed.

Optical modulators operating at near-infrared wavelengths are of interest for a variety of applications including bidirectional communications and optical interconnects. The fabrication of 1.06 {micro}m and 1.32 {micro}m operating wavelength strained-layer-superlattice vertical-cavity optoelectronic modulators requires the formation of a p-type ohmic contact to the InAlAs/InGaAs quarter-wave bottom mirror stack. In this study, BeAu and TiPtAu p-type ohmic contact metallization schemes were evaluated for use on molecular beam epitaxy (MBE) grown In{sub .10}Al{sub .90}As/In{sub .12}Ga{sub .88}As and In{sub .32}Al{sub .68}As/In{sub .33}Ga{sub .67}As device heterostructures. Recessed and nonrecessed transmission line measurement (TLM) structures were fabricated and evaluated as a function of rapid thermal anneal (RTA) temperatures over the range of 360 C--420 C. Atomic force microscopy (AFM) was used to determine the surface morphology of each sample for evidence of metal or material degradation. For contacts directly on InGaAs layers, TiPtAu contacts had relatively high specific contact resistance values of {rho}{sub c} {approximately} 3 {times} 10{sup {minus}4} {Omega}cm{sup 2} and displayed no dependence on the anneal. The BeAu contacts had minimum specific contact resistance values of {rho}{sub c} {approximately} 5 {times} 10{sup {minus}7} {Omega}cm{sup 2} but showed evidence of degradation at higher temperatures. Contacts directly made to InAlAs layers had minimum specific contact resistances of {rho}{sub c} {approximately} 4 {times} 10{sup {minus}5} {Omega}cm{sup 2} and were improved slightly with the addition of a thin GaAs layer.

Adhesion strength and surface morphology of commonly used n- and p-type ohmic contacts and pad metallization schemes for GaAs were investigated. GeNiAu, GePdAu, BeAu, and TiPtAu (being studied as potential ohmic contacts for internal optoelectronic devices) had quantitiative measurements made using wire bond pull testing to determine adhesion. Bond pad metals deposited as evaporated TiAu, TiPtAu, and 2-5 micron thick electroplated Au deposited on both semi-insulating GaAs and on Si{sub 3}N{sub 4}/GaAs were evaluated independently from the ohmic contact metals. In all samples was observed a strong correlation between surface treatment, surface morphology, wire bondability, and bond strength. Very high bond strengths (pull test average values above 6.5 grams force with 25 micron dia Au wire) wereobtained for n-type, p-type, and bond pad metals. Average values of 8.0 gram force were achieved with two-step GeAu/NiAu/TiPtAu metallization, while one-step deposition yielded poorer values. Adhesion was also monitored after aging at 250 C in air for four different times up to 60 hr by wire bond pull testing, with little degradation occurring.

SiC Schottky rectifiers with moderate breakdown voltages of ∼450 V and with either WSiX or Ni rectifying contacts were irradiated with Co-60 γ-rays to doses up to ∼315 Mrad. The Ni/SiC rectifiers show severe reaction of the contact after irradiation at the highest dose, badly degrading the forward current characteristics and increasing the on-state resistance by up to a factor of 6 after irradiation. By sharp contrast, the WSiX/SiC devices show little deterioration of the contact with the same conditions and changes in on-state resistance of

A comparison was made of specific contact resistivity and morphology of Ti/Al/Pt/WSi/Ti/Au and Ti/Al/Pt/W/Ti/Au ohmic contacts to AlGaN/GaN heterostructures relative to the standard Ti/Al/Pt/Au metallization. The W- and WSi-based contacts show comparable specific resistivities to that of the standard contact on similar layer structures, reaching minimum values of ∼10−5 Ω cm2 after annealing in the range 850–900 °C. However, the W- and WSi-based contacts exhibit much smoother surface morphologies, even after 950 °C annealing. For example, the root-mean-square roughness of the Ti/Al/Pt/WSi/Ti/Au contact annealed at 950 °C was unchanged from the as-deposited values whereas the Ti/Al/Pt/Au contact shows significant deterioration of the morphology under these conditions. The improved thermal stability of the W- and WSix-based contacts is important for maintaining edge acuity during high-temperature operation.

Unpassivated AlGaN/GaN high-electron-mobility transistors show significant gate lag effects due to the presence of surface states in the region between the gate and drain contact. Low-temperature (100 °C) layers of MgO or Sc2O3 deposited by plasma-assisted molecular-beam epitaxy are shown to effectively mitigate the collapse in drain current through passivation of the surface traps. These dielectrics may have advantages over the more conventional SiNX passivation in terms of long-term device stability.

In this work, we describe the most recent progress towards the device modeling, fabrication, testing and system integration of active resonant subwavelength grating (RSG) devices. Passive RSG devices have been a subject of interest in subwavelength-structured surfaces (SWS) in recent years due to their narrow spectral response and high quality filtering performance. Modulating the bias voltage of interdigitated metal electrodes over an electrooptic thin film material enables the RSG components to act as actively tunable high-speed optical filters. The filter characteristics of the device can be engineered using the geometry of the device grating and underlying materials. Using electron beam lithography and specialized etch techniques, we have fabricated interdigitated metal electrodes on an insulating layer and BaTiO3 thin film on sapphire substrate. With bias voltages of up to 100V, spectral red shifts of several nanometers are measured, as well as significant changes in the reflected and transmitted signal intensities around the 1.55um wavelength. Due to their small size and lack of moving parts, these devices are attractive for high speed spectral sensing applications. We will discuss the most recent device testing results as well as comment on the system integration aspects of this project.

We have successfully demonstrated an integrated optical system for collecting the fluorescence from a trapped ion. The system, consisting of an array of transmissive, dielectric micro-optics and an optical fiber array, has been intimately incorporated into the ion-trapping chip without negatively impacting trapping performance. Epoxies, vacuum feedthrough, and optical component materials were carefully chosen so that they did not degrade the vacuum environment, and we have demonstrated light detection as well as ion trapping and shuttling behavior comparable to trapping chips without integrated optics, with no modification to the control voltages of the trapping chip., Comment: 14 pages, 12 figures

In this paper, we describe progress towards a multi-color spectrometer and radiometer based upon an active resonant subwavelength grating (RSG). This active RSG component acts as a tunable high-speed optical filter that allows device miniaturization and ruggedization not realizable using current sensors with conventional bulk optics. Furthermore, the geometrical characteristics of the device allow for inherently high speed operation. Because of the small critical dimensions of the RSG devices, the fabrication of these sensors can prove challenging. However, we utilize the state-ofthe-art capabilities at Sandia National Laboratories to realize these subwavelength grating devices. This work also leverages previous work on passive RSG devices with greater than 98% efficiency and ~1nm FWHM. Rigorous coupled wave analysis has been utilized to design RSG devices with PLZT, PMN-PT and BaTiO3 electrooptic thin films on sapphire substrates. The simulated interdigitated electrode configuration achieves field strengths around 3×10 7 V/m. This translates to an increase in the refractive index of 0.05 with a 40V bias potential resulting in a 90% contrast of the modulated optical signal. We have fabricated several active RSG devices on selected electro-optic materials and we discuss the latest experimental results on these devices with variable electrostatic bias and a tunable wavelength source around 1.5µm. Finally, we present the proposed data acquisition hardware and system integration plans.

We design and fabricate guided-mode resonant subwavelength gratings using an active layer of barium titanate. Loss mechanisms in the metal and in the guiding layer are investigated. Modeling and experimental results are shown.

In situ gravimetric measurements and microscopic examinations were used to determine the mechanisms of oxygen removal from synthetic ilmenite disks between 823 and 1353 K. Under a hydrogen atmosphere, iron was observed to form a layer of low porosity on the surface of samples early in the reduction. This created diffusion limitations for hydrogen to the reaction front and for the escape of water vapor. A shrinking core reduction model, modified to include the growth of this iron film, was capable of predicting the conversion-time relationships of ilmenite samples. An activation energy of 43.2 ± 2.6 kcal/gmole was determined to be representative of reaction control over the temperature range 823–1023 K.

There is a clear difference in cook‐off vulnerability between highly‐loaded pressed compositions such as LX‐14 (pressed 95.5% HMX/4.5% binder), which yield violent responses, and cast compositions with low loadings, such as CPX 301 (85% RDX/15% HTPB), which yield relatively mild responses. These two classes of composition differ primarily in the quantity of binder, and in the manufacturing method used in production. An experimental study was conducted in an attempt to determine the filling proportion beyond which violent responses are observed. Here we describe a series of small‐scale cook‐off experiments which studied pressed compositions of 88%, 91%, 95% and 96% HMX, mixed with cured, cross‐linked HTPB. The experiments used a novel glass‐windowed test vehicle, instrumented internally with thermocouples. A trend of increasing event violence with increasing proportion of HMX was found, although in none of the experiments was mass reaction recorded. The results from these experiments are discussed.

GaN-based microwave power amplifiers have been identified as critical components in Sandia's next generation micro-Synthetic-Aperture-Radar (SAR) operating at X-band and Ku-band (10-18 GHz). To miniaturize SAR, GaN-based amplifiers are necessary to replace bulky traveling wave tubes. Specifically, for micro-SAR development, highly reliable GaN high electron mobility transistors (HEMTs), which have delivered a factor of 10 times improvement in power performance compared to GaAs, need to be developed. Despite the great promise of GaN HEMTs, problems associated with nitride materials growth currently limit gain, linearity, power-added-efficiency, reproducibility, and reliability. These material quality issues are primarily due to heteroepitaxial growth of GaN on lattice mismatched substrates. Because SiC provides the best lattice match and thermal conductivity, SiC is currently the substrate of choice for GaN-based microwave amplifiers. Obviously for GaN-based HEMTs to fully realize their tremendous promise, several challenges related to GaN heteroepitaxy on SiC must be solved. For this LDRD, we conducted a concerted effort to resolve materials issues through in-depth research on GaN/AlGaN growth on SiC. Repeatable growth processes were developed which enabled basic studies of these device layers as well as full fabrication of microwave amplifiers. Detailed studies of the GaN and AlGaN growth of SiC were conducted and techniques to measure the structural and electrical properties of the layers were developed. Problems that limit device performance were investigated, including electron traps, dislocations, the quality of semi-insulating GaN, the GaN/AlGaN interface roughness, and surface pinning of the AlGaN gate. Surface charge was reduced by developing silicon nitride passivation. Constant feedback between material properties, physical understanding, and device performance enabled rapid progress which eventually led to the successful fabrication of state of the art HEMT transistors and amplifiers.

In this paper, high temperature hydrogen gas sensors with GaN and SiC based Schottky diodes were studied using Pd and Pt as Schottky contacts. Here we investigated thermal stability of W and WSi based Schottky metals for high temperature gas sensing. Schottky characteristics were observed for Au/Ti/W/SiC up to 900/spl deg/C annealing.

A contacted electroreflectance technique was used to characterize the electronic properties of AlGaN/GaN heterostructure field-effect transistors (HFETs). By studying variations in the electroreflectance with applied electric field, spectral features associated with the AlGaN barrier, the 2-dimensional electron gas at the interface, and bulk GaN were observed. Barrier-layer composition and electric field were determined from the AlGaN Franz-Keldysh oscillations. Comparing HFETs grown on SiC and sapphire substrates, the measured AlGaN polarization electric field (0.25±0.05 MV/cm) approached that predicted by a standard model (0.33 MV/cm) for the higher mobility HFET grown on SiC.

In this paper we report new experimental results on the detonation characteristics of nitromethane containing high volume percentages of essentially inert additives. In particular, we have studied the detonation of packed beds of small spherical glass and aluminium particles saturated with pure nitromethane. These mixes are found to have reduced detonation velocities and critical diameters compared to the liquid explosive alone. We conclude with a general discussion of the propagation mechanism in such materials.

Great strides have been made in the development of ultraviolet LED materials and devices. Power levels in the near UV (below 390 nm) have been improved from the 10 W to the 1 mW level through improvements in the growth and design of AlInGaN alloys. High frequency AlGaN/GaN HEMTs have been developed with ft of 65 GHz and fmax of 85 GHz, all while attaining breakdown voltage greater than 100 V. A new breakthrough in the lateral overgrowth of GaN materials promises to further improve these devices.

Massively parallel optical interconnects are appropriate to ease the data bandwidth bottleneck that will occur in future computing applications. Vertical cavity surface emitting lasers (VCSELs) are promising sources for emerging 2D optical systems such as free space and guided wave optical interconnects. We discuss the development of high performance VCSEL arrays, including individually addressable and matrix addressable arrays. We also show the characteristics of GaAs microelectronic driver and photoreceiver chips that have been designed to interface with Si-based CMOS circuitry. Finally, the potential of these source and receiver modules for use in free space or guided wave parallel channel optical interconnect architectures will be described.

Vertical cavity surface emitting lasers (VCSELs) which operate in multiple transverse optical modes have been rapidly adopted into present data communication applications which rely on multi-mode optical fiber. However, operation only in the fundamental mode is required for free space interconnects and numerous other emerging VCSEL applications. Two device design strategies for obtaining single mode lasing in VCSELs based on mode selective loss or mode selective gain are reviewed and compared. Mode discrimination is attained with the use of a thick tapered oxide aperture positioned at a longitudinal field null. Mode selective gain is achieved by defining a gain aperture within the VCSEL active region to preferentially support the fundamental mode. VCSELs which exhibit greater than 3 mW of single mode output power at 850 nm with mode suppression ratio greater than 30 dB are reported.

Ultra high-speed digital photography has been used to record the onset and build-up of reaction in nitromethane charges that have been impacted by steel fragments. The nitromethane charges were housed in PMMA cylinders and back-lit using conventional flash bulbs. Flat plates of aluminum were glued to one end of the cylinder and PMMA plates to the other. The completed charge was positioned to allow normal impact of the projectiles through the aluminum barrier plate. The events were filmed using an Imacon 468, ultra high-speed digital image system, capable of framing at up to 100 million pictures per second. Using this system it was possible to record detailed photographic information concerning the onset and growth of reaction due to shock initiation of the nitromethane charges. The results obtained to date are consistent with the established concepts for initiation of homogeneous and heterogeneous materials.

Optocouplers are used for a variety of applications aboard spacecraft including electrical isolation, switching and power transfer. Commercially available light emitting diode (LED)-based optocouplers have experienced severe degradation of light output due to extensive displacement damage occurring in the semiconductor lattice caused by energetic proton bombardment. A new optocoupler has been designed and fabricated which utilizes vertical cavity surface emitting laser (VCSEL) and resonant cavity photodetector (RCPD) technologies for the optocoupler emitter and detector, respectively. Linear arrays of selectively oxidized GaAs/AlGaAs VCSELS and RCPDS, each designed to operate at a wavelength of 850nm, were fabricated using an airbridge contacting scheme. The airbridged contacts were designed to improve packaging yields and device reliability by eliminating the use of a polyimide planarizing layer which provided poor adhesion to the bond pad metallization. Details of the airbridged optocoupler fabrication process are reported. Discrete VCSEL and RCPD devices were characterized at temperatures between {minus}100 to 100 C. Devices were packaged in a face-to-face configuration to form a single channel optocoupler and its performance was evaluated under conditions of high-energy proton bombardment.

Fabrication of group-Ill nitride electronic and photonic devices relies heavily on the ability to pattern features with anisotropie profiles, smooth surface morphologies, etch rates often exceeding 0.5 μm/min, and a low degree of plasma-induced damage. Patterning these materials has been especially difficult due to their high bond energies and their relatively inert chemical nature as compared to other compound semiconductors. However, high-density plasma etching has been an effective patterning technique due to ion fluxes which are 2 to 4 orders of magnitude higher than conventional RIE systems. GaN etch rates as high as -1.3 μm/min have been reported in ECR generated ICI plasmas at -150 V dc-bias. In this study, we report high-density GaN etch results for ECR- and ICP-generated plasmas as a function of Cl2- and BCl3-based plasma chemistries.

MgO or Sc 2 O 3 passivated AlGaN/GaN high electron mobility transistors (HEMTs) were irradiated with 40 MeV protons at a dose equivalent to ∼10 years in low-earth orbit. Very little change in drain-source current, transconductance, or diode ideality factor was observed under these conditions, but the reverse breakdown increased due to a decrease in channel electron density. In addition, no significant change was observed in the drain-source current under pulsed conditions, indicating that the proton irradiation did not alter the effectiveness of the MgO and Sc 2 O 3 in passivating surface states.

The authors describe an (InGaAl)As/InGaAs vertical-cavity optical transmission modulator operating at 1.32 /spl mu/m, and having a single pass contrast /spl Delta/T/T of 24% at

The tunnel cathode consists of a metal‐insulator‐metal sandwich in which the electrons tunnel through the insulator material. This paper presents an analysis of the noise associated with the space‐charge waves of a beam emitted from such a cathode. The beam noise temperature for a refrigerated tunnel cathode is shown to be 2730 δ, where δ is the value in volts of a built‐in energy window for the emitted electrons. The value of δ is adjustable by means of a dc potential. Assuming a beam noise temperature of 30°K, the current density is calculated for a variety of cathode parameters. A discussion is presented of the significance of the parameters and of the difficulties which would be encountered in constructing such cathodes for low noise.

Large area, HgCdTe MW photovoltaic detectors have been developed at Honeywell Electro-Optics Division for the NASA-HALOE instrument. This instrument is scheduled for operation on the Upper Atmospheric Research Satellite (UARS). The photodiodes will be TE cooled and were designed to operate in the 5.1 μm - 5.4 μm band at 185 K to measure Nitric Oxide (NO) concentrations in the atmosphere. To achieve the D* goal of 6 x 109 cm-Hz1/2/W and to meet the spatial responsivity uniformity specification of ± 5% across the 0.6 mm diameter, active area required 15 μm thick devices and a full backside common contact,. Reflections from the backside contact doubled the effective thickness of the detectors. Optical interference from reflections was eliminated with a dual layer front surface A/R coating. Bakeout reliability was optimized by having Au metallization for both n and p interconnects. Detailed performance data and a model for the optical stack are presented.

The wide band gap group-III nitride materials continue to generate interest in the semiconductor community with the fabrication of green, blue, and ultraviolet light emitting diodes (LEDs), blue lasers, and high temperature transistors. Realization of more advanced devices requires pattern transfer processes which are well controlled, smooth, highly anisotropic and have etch rates exceeding 0.5 μm/min. The utilization of high-density chlorine-based plasmas including electron cyclotron resonance (ECR) and inductively coupled plasma (ICP) systems has resulted in improved etch quality of the group-III nitrides over more conventional reactive ion etch (RIE) systems.

Inductively Coupled Plasma (ICP) sources are extremely promising for large-area, highion density etching or deposition processes. In this review we compare results for GaAs and GaN etching with both ICP and Electron Cyclotron Resonance (ECR) sources on the same singlewafer platform. The ICP is shown to be capable of very high rates with excellent anisotropy for fabrication of GaAs vias or deep mesas in GaAs or GaN waveguide structures.