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We report our work in developing microelectromechanical systems (MEMS)-based Ultra High Frequency (UHF) AT-cut quartz monolithic crystal filters operating between 350 and 400 MHz for integration with Si electronics for highly compact Radio Frequency (RF) front-end electronics. Our narrow bandwidth (0.2%) high $Q$ filters have measured insertion losses of −2 dB with temperature stability of roughly 50 ppm over a temperature range of 10°– 80°C. Wafer-level optical metrology and ion milling techniques have been developed to provide enhanced accuracy of the filter center frequency and resonator parameters for optimized performance and improved yields. [2015-0163]

Quartz MEMS resonators are attractive for use in oscillators for frequency control applications by virtue of their reduced cost, size, weight, and power (CSWaP), combined with the potential for integration with electronics. We present an ultra-miniature, oscillator (1 mm3 total volume) built with a thickness shear mode quartz resonating element integrated with a SiGe BiCMOS sustaining ASIC to achieve a fundamental-mode UHF operation of >800 MHz. This low-power (

Historically, compound semiconductors have enjoyed the benefit of material properties that lend themselves to high performance electron devices, but the ability to fabricate complex, high transistor count ICs is limited by the relative immaturity of the material system and small commercial market. Silicon based devices have made significant advances in device performance, but have not yet matched compound semiconductor device performance. However, a large commercial market has allowed the silicon system to mature and produce billion transistor count ICs in high volume. It would be advantageous to combine the merits of both compound semiconductors and silicon based CMOS/BiCMOS to enable a new class of high performance ICs. This work will review HRL's efforts in wafer scale integration of an advanced 250nm, 350GHz fT/fMAX InP DHBT technology with RF-CMOS technologies whose device proximity; heterogeneous interconnect density; and additional technology features both leverage and provide additional value to conventional silicon technologies.

The significant optical and size benefits of using a curved focal surface for imaging systems have been well studied yet never brought to market for lack of a high-quality, mass-producible, curved image sensor. In this work we demonstrate that commercial silicon CMOS image sensors can be thinned and formed into accurate, highly curved optical surfaces with undiminished functionality. Our key development is a pneumatic forming process that avoids rigid mechanical constraints and suppresses wrinkling instabilities. A combination of forming-mold design, pressure membrane elastic properties, and controlled friction forces enables us to gradually contact the die at the corners and smoothly press the sensor into a spherical shape. Allowing the die to slide into the concave target shape enables a threefold increase in the spherical curvature over prior approaches having mechanical constraints that resist deformation, and create a high-stress, stretch-dominated state. Our process creates a bridge between the high precision and low-cost but planar CMOS process, and ideal non-planar component shapes such as spherical imagers for improved optical systems. We demonstrate these curved sensors in prototype cameras with custom lenses, measuring exceptional resolution of 3220 line-widths per picture height at an aperture of f/1.2 and nearly 100% relative illumination across the field. Though we use a 1/2.3" format image sensor in this report, we also show this process is generally compatible with many state of the art imaging sensor formats. By example, we report photogrammetry test data for an APS-C sized silicon die formed to a 30$^\circ$ subtended spherical angle. These gains in sharpness and relative illumination enable a new generation of ultra-high performance, manufacturable, digital imaging systems for scientific, industrial, and artistic use.

HRL Laboratories is part of an intense research and development effort to leverage the enormously advanced infrastructure of Si CMOS and the high performance of diverse electronic and photonic devices in an integrated technology. While System in a Package (SiP) and System on a Chip (SoC) approaches involve chips produced in their native foundries and subsequent integration using hybridization or multi-chip modules, HRL has pioneered approaches where partially completed wafers of diverse technologies are integrated using highly intimate placement and heterogeneous interconnects to enable transistor-level integration. Novel ICs have been produced in InP BiCMOS and CMOS memristor-integrated technologies. Unprecedented design flexibility is being enabled with intimate integration of GaN HEMTs together with InP and CMOS.

Progress on achieving reproducible growth of high performance, dual-band IR detector structures in HgCdTe grown by molecular beam epitaxy (MBE) is described. The reproducibility achieved in the MBE growth of n-p-n device structures comprising HgCdTe epitaxial layers with different composition and doping characteristics was evaluated from the run-to-run precision in the alloy composition, dopant concentration and dislocation density. For a series of 25 growth runs, the standard deviation of the alloy composition in the n-type absorbing layer was 0.002; the yield for the in situ n- and p-type doping process was > 95%; and the average dislocation density was < 5 x 10 5 cm -2 . In situ optical diagnostics, including spectroscopic ellipsometry and an optical absorption flux monitor were used for the real-time determination of the alloy composition and Cd flux during MBE growth of the two-color device structures. Focal plane arrays with 128 x 128 elements were fabricated for the simultaneous detection of two sub-bands in the MWIR spectrum. Average R o A values exceeding 1 x 10 6 and 2 x 10 5 Ω cm 2 were measured at 77 K for diodes operating at 4.0 and 4.5 μm, respectively, and the quantum efficiency was greater than 70% in each band. These results on MBE growth and device performance demonstrate that HgCdTe MBE technology is poised for the modest-scale production of advanced IR devices.

We describe an integrated real-time sensing and control system for monitoring and controlling substrate temperature, layer composition, and effusion cell flux during molecular beam epitaxial growth of HgCdTe epilayers for advanced IR detectors. Substrate temperature is monitored in real-time using absorption-edge spectroscopy, allowing the temperature to be controlled within 1.5°C of the desired setpoint. In situ spectroscopic ellipsometry (SE) is used for monitoring HgCdTe layer composition in real-time. A comprehensive temperature- and composition-dependent dielectric function database has been recorded which allows the accurate and precise determination of Hg1−xCdxTe layer composition over a wide range of x-values, from 0.2 to 0.42. The composition changes inferred from real-time SE measurements obtained during growth of a two-layer structure are in excellent agreement with composition profiles obtained using post-growth secondary ion mass spectroscopy analysis. The accuracy and precision of SE measurements conducted over multiple growth runs are shown to be suitable for robust SE-based composition control. Changes in the Cd flux produced by a CdTe effusion cell are detected using an atomic optical absorption method. This method allows changes in HgCdTe layer composition to be correlated directly with variations in Cd flux. All of the in situ sensors are linked using a custom software framework to provide the foundation for real-time monitoring and control of HgCdTe MBE growth of high performance infrared detector structures over a wide range of compositions, layer thicknesses, and substrate temperatures.

The use of a multiple-sensor control system to regulate in real-time the growth of thick, lattice-matched epitaxial films of InGaAs and InAlAs on InP substrates is described. The application of transmission-mode absorption-edge spectroscopy for in situ substrate temperature sensing, and spectroscopic ellipsometry for epilayer composition and thickness are discussed, and examples are given demonstrating precision and accuracy consistent with the fabrication of devices such as heterojunction bipolar transistors that require thick (>1.5 μm) InGaAs layers. Feedback regulation of substrate temperature to ±1°C and epilayer composition (alloy fraction) to ±0.002 are demonstrated using a cascade-PID control scheme in which the sensor is used in a software-based outer control loop. Growth of a complete HBT using sensor-based feedback control of substrate temperature, composition and epilayer thickness is described.

Molecular beam epitaxy was employed for the growth of HgCdTe-based n-p+-n device structures on (211)B oriented CdZnTe substrates. The device structures were processed as mesa isolated diodes, and operated as back-to-back diodes for the simultaneous detection of two closely spaced sub-bands in the mid-wave infrared spectrum. The devices were characterized by R0A values in excess of 5 × 105 Ω cm2 at 78K, at f/2 fov and quantum efficiencies greater than 70% in each band. Infrared imagery from a focal plane array with 128 × 128 pixels was acquired simultaneously from each band at temperatures between 77 to 180K, with no observable degradation in the image quality with increase in temperature.

Next-generation HgCdTe infrared detectors and detector arrays require the growth of multilayer heterojunction structures with precisely controlled alloy composition and doping levels and minimal defect densities. Molecular beam epitaxy (MBE) provides the ability to produce such structures. However, in the absence of a real-time, in situ control methodology the extreme sensitivity of HgCdTe layer quality and doping efficiency on fundamental MBE variable such a substrate temperature and effusion cell flux provide serious challenges to the uniform and reproducible growth of such structures. In this paper, we describe an integrated, multi-sensor approach for monitoring and controlling the variables that are most important for MBE growth of HgCdTe device structures used in advanced multi-color infrared detectors and high speed, low-noise avalanche photodiodes. Substrate temperature, effusion cell flux, and layer composition are monitored using absorption-edge spectroscopy (ABES), optical flux monitoring (OFM), an spectroscopic ellipsometry (SE), respectively. Flexible, custom software has been developed and implemented for analysis of sensor inputs and feedback control of the MBE system in response to those inputs. The sensors and their application to growth of HgCdTe will be described, and the use of a custom software framework for data analysis and system control will be discussed.

A 1 GHz AT-cut quartz thickness shear mode resonator is modeled for the first time with thermally induced bonding stresses and their effect on the device frequency-temperature (f-T) characteristic. Without the details of the bonding configuration, modeling indicates the f-T characteristic slightly rotates as a function of the change in stiffness of a simplified absorbing mount. However, if details of the bonding configuration are included, our modeling predicts the potential for a significant distortion in the f-T curve. High or varying stress over temperature in the device active region is found to lead to an undesirable increase in the f-T slope. The origin of the active region stress can be varied, but in practice it frequently originates from a temperature dependent bonding stress, or from fabrication steps such as metal depositions. In this paper we highlight the magnitude of the thermal stress effect on the f-T curve, and offer design methods that mitigate the thermally induced bonding stress by de-coupling the active resonator area from high stress regions of the quartz device.

A quartz resonator operating at 995 MHz in the fundamental mode has been characterized in a closed loop oscillating system under different drive levels to determine its nonlinear behavior and optimum phase noise performance. The best phase noise achieved was -106 dBc/Hz at a 1 kHz offset frequency. The same quartz technology was used to build VCXOs in both the Colpitts and Pierce configurations at several frequencies above 650 MHz. The lowest phase noise level achieved in the Colpitts configuration operating at 705 MHz is -111 dBc/Hz at a 1 kHz offset frequency while a Pierce Oscillator operating at 662 MHz achieved a phase noise of -112.8 dBc/Hz at the same offset. Power consumption in these VCOs is typically on the order of 30-90 mW.

Stable local oscillators with low phase noise are extremely important elements in high performance communication and navigation systems. We present the development of compact UHF-band frequency sources capable of maintaining low phase noise for handheld portable systems. We also explored nonlinearity in MEMS resonators and attempted to use nonlinear dynamics to enhance phase noise performance. Using the quartz MEMS technology, we have thus far demonstrated a 635 MHz oscillator with -112 dBc/Hz phase noise at 1 kHz offset frequency. The controlled oscillation of this nonlinear Duffing resonator in a closed-loop system with improved phase noise is described.

A robust process has been developed for the reproducible growth of in-situ doped Hg1−xCdxTe:As alloys by molecular beam epitaxy. Net hole concentrations in excess of 5 x 1017 cm−3, with peak mobilities >200 cm2/Vs were measured in Hg0.74Cd0.26Te:As films. The p-type layers were twin-free and consistently exhibit narrow x-ray rocking curves (

Stable local oscillators with low phase noise are extremely important elements in high performance military communication and navigation systems. We present the development of compact UHF-band frequency sources capable of maintaining low phase noise under high accelerations or vibrations and over a wide temperature range for handheld portable systems. We also explored nonlinearity in MEMS resonators and attempted to use nonlinear dynamics to enhance phase noise performance. Using the quartz MEMS technology, we have thus far demonstrated a 645 MHz Pierce oscillator with -113 dBc/Hz phase noise at 1 kHz offset with acceleration sensitivity of 5x10 -10 /g. The controlled oscillation of a nonlinear Duffing resonator in a closed-loop system with improved phase noise is described.

Characterization of a quartz resonator operating at 553 MHz in a closed loop oscillating system has been performed under various drive levels to characterize its nonlinear behavior. The voltage and current were measured across the resonator using differential active probes and used to calculate the magnitude of the admittance under drive. Our results show that nonlinear resonator operation widens the bandwidth of low phase noise operation. At the low frequency end of the operating range, where overall phase noise is degraded, phase noise improvement is ∼ 20dB. However, the overall phase noise levels do not improve significantly over the linear case.

InP Bi-CMOS technology capable of wafer-scale device-level heterogeneous integration (HI) of InP HBTs and CMOS has been developed. With this technology, full simultaneous utilization of III–V device speed and CMOS circuit complexity is possible. Simple ICs and test structures have been fabricated, showing no significant CMOS or HBT degradation and high heterogeneous interconnect yield. The heterogeneously integrated differential amplifiers with record performance and HBTs with f T =400GHz were obtained. Thermal vias to the Si substrate provide sufficient heat path to lower HI HBT thermal resistances close to on-InP values. Resulting circuits maintain maximum CMOS integration density and HBT performance, while keeping the heterogeneous interconnect length below 5µm.

InAs-based HBT technology was discussed. Several of the available fabrication processes were presented, as well as the device performance obtained from some of the options.

Use of a cracked Sb source and a postgrowth anneal procedure has been found to yield significant improvements in optical efficiencies of GaInSb/InAs superlattices grown by molecular beam epitaxy. Appreciable 5 μm band‐to‐band luminescence has been observed at room temperature, and stimulated emission at 3.2 μm has been demonstrated in an optically pumped structure. Intrinsic properties of this class of superlattices favor them for application as efficient infrared lasers operating at comparatively high temperatures.

InAs-based heterojunction bipolar transistors (HBTs) have great potential for applications requiring high speed and low power integrated circuits. Significant advantages of the InAs material properties over those of InGaAs and GaAs have motivated recent research into InAs-based HBTs. The advantages of InAs include a low bandgap, low electron effective mass, high peak velocity and high electron mobility. InAs/InAsP and InAs/InAlAs SHBT and DHBTs have been grown on both InAs and InP substrates. Initial results from InAsP/InAs HBTs grown on InAs and transferred to sapphire substrates show comparable performance to the well established InGaAs/InAlAs HBT. An Ft of 181 GHz has been measured at a collector-emitter voltage of 0.6 V and collector current of 7.6 mA. for 1/spl times/3 /spl mu/m/sup 2/ sized emitter devices. Divide-by-16 circuits have been fabricated to demonstrate the basic building blocks for digital ICs.

The use of in situ sensors to achieve real-time control of MBE growth is a rapidly evolving technology that promises to revolutionize MBE in terms of process repeatability and first-pass success, and consequently, to improve the overall yield and reduce the cost of the process. For the growth of InGaAs and related materials on InP, the most critical process variables to control are the substrate temperature and the epitaxial layer composition, insofar as both of these parameters can have dramatic effects on the performance of heterojunction bipolar transistors and other electronic and opto-electronic devices grown on InP. To achieve robust real-time control of the MBE growth process, we have constructed a multiple-sensor control system comprising in situ sensors for substrate temperature, effusion cell fluxes, and epitaxial layer composition and thickness, along with advanced software to manage the sensor information and execute sensor-feedback control algorithms. The design and operation of this system is described and its performance is illustrated through examples of real-time sensor-feedback control of substrate temperature and layer composition during the growth of InGaAs on InP.

Since its initial synthesis and investigation more than 40 years ago, the HgCdTe alloy semiconductor system has evolved into one of the primary infrared detector materials for high-performance infrared focal-plane arrays (FPA) designed to operate in the 3-5 mm and 8-12 mm spectral ranges of importance for thermal imaging systems. Over the course of the past decade, significant advances have been made in the development of thin-film epitaxial growth techniques, such as molecular-beam epitaxy (MBE), which have enabled the synthesis of IR detector device structures with complex doping and composition profiles. The central role played by in situ sensors for monitoring and control of the MBE growth process are reviewed. The development of MBE HgCdTe growth technology is discussed in three particular device applications: avalanche photodiodes for 1.55 +m photodetection, megapixel FPAs on Si substrates, and multispectral IR detectors.

KrF excimer laser irradiation of CdTe at fluences below the melt threshold (≤75 mJ/cm2) removes surface layers and produces reversible changes in the surface composition that depend upon the laser fluence and number of laser pulses delivered to the surface. At fluences above ∼40 mJ/cm2 a Te‐rich layer is obtained. A stoichiometric composition can be restored by irradiation at reduced laser fluence. The primary desorption products are Cd and Te2, and the velocities of these species are well described by a Maxwellian distribution. The fluence‐dependent changes in CdTe surface composition are consistent with a photothermal mechanism based on the competition between formation and desorption of Te2 and desorption of Cd atoms from the laser‐irradiated surface.

In this paper we discuss the use of optical-based flux monitoring (OFM) for real-time control of atomic antimony fluxes for applications in molecular beam epitaxy. Atomic antimony beams were generated using a two-zone cracking effusion cell. The product distribution of the source was characterized using a time-of-flight mass spectrometer employing resonance-enhanced laser ionization. A double-pass OFM system has been developed to monitor the atomic antimony beam that is capable of precise flux measurement during MBE growth.

It is shown that the composition and structure of CdTe and CdS surfaces can be reversibly controlled by excimer laser irradiation at fluences below the melting threshold. The removal rate is observed to depend exponentially on laser fluence up to the melting threshold. The translational energies of products desorbed from laser-irradiated CdTe surfaces were determined using time-of-flight spectrometry and are well-described by a Maxwellian velocity distribution. The dynamics of the photo-stimulated desorption process are correlated with the laser-induced changes in composition, and it is shown that the data are consistent with a thermal mechanism for desorption. A model is introduced which describes the reversible, fluence-dependent changes in composition and structure in terms of the kinetic competition between formation and desorption processes at the semiconductor surface.

We have investigated the dynamics of KrF excimer laser ablation of CdTe and the fluence dependent changes in surface stoichiometry that accompany the laser ablation process. The composition of the CdTe surface was reversibly controlled between stoichiometric and a Te-rich condition by varying the laser fluence over the range from 15–65 mJ/cm2. The primary species ejected from the irradiated surface were Cd atoms and Te2 molecules. Their velocity distributions as measured by time-of-flight mass spectrometry were found to be Maxwellian. From the analysis of the velocity distributions, the preferential desorption of surface atoms, and the reversible nature of the process, we conclude that the desorption is due to a photo-thermal mechanism which mediates the competition between Te2 formation and desorption and the desorption of Cd atoms.

A study of the changes in surface structure and composition of CdTe(100) irradiated by 248 nm excimer laser radiation in the fluence range 18-75 mJ/cm2 is presented. Material is removed from the CdTe surface at all fluences, but above a threshold fluence of 40 mJ/cm2 the surface becomes Te-rich. Reflection high energy electron diffraction measurements indicate that the original 2×1 surface reconstruction is converted to a 1×1 pattern at fluences < 40 mJ/cm2. At exposures which generate a Te-rich surface a RHEED pattern is not observed. Temperature programmed desorption experiments show that weakly bound Tex exists on the surface after exposure at all fluences used in this study. A correlation of Auger data, desorption lineshapes, and model calculations suggest that the excess Te forms three dimensional islands on the surface.

Detection of Te atoms in the ground 3P2,1,0 states has been accomplished using two-photon laser-induced fluorescence (LIF) and “2 + 1” multiphoton ionization (MPI). Te atoms were produced by multiphoton dissociation of (C2H5)2Te in the region 358–395 nm. The LIF and MPI experiments utilize selective excitation of the 6p 3PJ′←5p 3PJ″ and 7p 3PJ′←5p 3P2 transitions by two-photon absorption. Line strength intensities for the individual J′ ← J″ fine structure pairs of the 6p 3PJ′ ← 5p 3PJ″ two-photon transitions were calculated and compared to the LIF data. Intensities of these transitions of Te atoms are compared to analogous 3P ← 3P transitions in S and O atoms.

Two-photon laser-induced fluorescence and “2+1” multiphoton ionization detection of silicon ( 3 P j″ , 1 D 2 ) atoms was accomplished using the 4 3 P J' ←3 3 P j″ , 4 3 S 1 → 3 3 P J′ , and the 4 1 D 2 → 3 1 D 2 resonant two-photon transitions. Silicon atoms were produced in their ground 3 P J″ ( J″ = 0,1,2) and first singlet 1 D 2 states by the multiphoton dissociation of Si(CH 3 ) 4 in the wavelength region 400–460 nm. Line strength intensities for the two-photon transitions originating from the 3 3 P J″ ( J″ = 0,1,2) states were calculated and compared to experimental values determining that the silicon ( 3 P J ″ ) atoms were produced in a statistical population distribution.

The growth of CdTe and HgTe by excimer laser‐assisted metalorganic vapor phase epitaxy on (100) GaAs at 165 °C is reported. HgTe layers have been grown on a 4000‐A buffer layer of CdTe on GaAs with the use of dimethylmercury and a new Hg‐containing source material, divinylmercury. A linear dependence of CdTe growth rate on laser power and reactant partial pressure has been observed using in situ time‐resolved reflectivity. The photodissociation mechanism for diethyltellurium (DETe) has been investigated using laser induced fluorescence. Results indicate that irradiation of DETe with 248‐nm photons produces ground‐state Te atoms by a single‐photon process.

We have successfully grown CdTe (111) on GaAs (100) at 165 °C using a 248 nm excimer laser to photodissociate dimethylcadmium and diethyltellurium in the gas phase. Good crystalline quality of the layers is confirmed by x‐ray diffractometry. Growth rates up to 2 μm/h have been recorded in real time using time‐resolved reflectivity. Auger analysis reveals that the films are stoichiometric throughout the thickness of the layer, and that carbon and oxygen contaminants are below the level of detectability. We have used laser‐induced fluorescence spectroscopy to examine the photodissociation mechanism of diethyltellurium and have observed a linear dependence of Te atom production on excimer laser power.

Dry, rapid etching of GaAs has been accomplished using an excimer laser (ArF, 193 nm) with HBr etching gas by photochemical initiation. Spatially uniform etch rates of up to 8 μm/min have been achieved on large‐area, masked substrates. Selective crystallographic etching is observed and controlled in the process.

UV radiation from an ArF laser has been used to perform large‐area etching of single‐crystal GaAs. The process is based on photochemical production of methyl or trifluoromethyl, and bromine radicals. The etching is anisotropic and features

In general photochemical (drying etching) process of thin films based on (UV) laser-initiated chemistry is difficult to investigate both mechanistically and kinetically. Some of the most important questions are concerned with the photo-formation of the reactive species and their (reactive) chemical interaction with the surface. The UV-laser assisted etching of SiO2 from photolysis of CH2 CHF is quite attractive for mechanistic studies of the etching process because of the relative simple (in-situ) application of IR (time-resolved) fluorescence and absorption techniques to monitor both the HF etchant and the SiF4 products within the gas-surface system. The strong oscillator and absorption strength of the HF molecules makes it possible to monitor its photo-production and follow the subsequent etching reaction with the SiO2 surface. Moreover, high resolution and sensitive diode laser absorption probes can be used to investigate the surface products (SiF4, SiF3, SiF2 and SiF) in the gas phase.

The use of laser assisted-chemistry for dry etching of electronic materials is described. Emphasis is placed on the use of laser-assisted reactions for large area processing. Review of the current technology is given for large area masked etching, UV-projection etching, and laser assisted reactive ion etching (RIE), and plasma etching.

The mechanism of the interaction of methyl radicals with Cd, Te, and CdTe surfaces has been studied in ultrahigh vacuum by Auger electron spectroscopy and thermal desorption mass spectrometry. Methyl radicals generated by the laser photodissociation of acetone at 193 nm efficiently etch both Te and Te-rich CdTe surfaces. However, there is no evidencefor reaction of methyl radicals with Cd or stoichiometric CdTe. A temperature dependencein the rate of methyl radical etching of Te-rich CdTe is related to a competition between acetone scavanging of radicals on the surface and reaction of radicals to form volatile metalorganics. Acetone itself has a small but finite reaction probability with Te and Te-rich CdTe surfaces.

Excimer laser-assisted MOVPE has been used to deposit thin films of CdTe (111) on GaAs (100) substrates. Auger spectroscopy indicates that the films are stoichiometric and that carbon and oxygen contamination are below the levels of detectability. Good crystalline quality of the layers is confirmed by x-ray diffractometry. Growth rates up to 2 /μm/hr have been recorded in real time using time-resolved reflectivity. The CdTe growth rate is found to have a linear dependence on reactant partial pressure and laser average power, but was independent of substrate temperature in the range of 150° C to 300* C. Laser-induced fluorescence spectroscopy has been used to determine that photolysis of diethyltellurium at 248 nm is a one photon process which produces ground state Te atoms. The flux of reactive species to the substrate surface has been probed by mass spectrometry. Evidence for the generation of monoethyltelluride, either by recombination or direct photolysis, is presented.

The UV photodissociations of dimethyltelluride (CH3)2Te and diethyltelluride (C2Hs)2Te have been investigated by state-selective detection. Nascent populations of Te(5p Pjw) atoms produced by the photodissociation process were monitored using laser-induced fluorescence following excimer laser (248 nm and 193 nm) photolysis. Experimental results for both molecules indicate that the photolysis at 248 nm produces Te atoms via a single photon process and that the liberated Te atoms populate only the 5p3P2 state. The photolysis of diethyltelluride at 193 nm has also been found to be a single photon process producing Te atoms distributed over the 3P2, 3P1, and Pø states in a ratio of 13:2:1, respectively.

Laser-assisted deposition of GaAs, AlAs and [AIGa]As thin films on Ge(100) substrates from trimethylgallium-trimethylarsenic and trimethylaluminumtrimethylarsenic Lewis acid-base adduct source materials is reported. A parametric study has been performed in which reactive gas pressure, substrate temperature, laser fluence, laser wavelength (248 nm or 193 nm). and orientation of the laser beam with respect to the substrate have been varied. In the case of irradiation parallel to the substrate, stoichiometric films of GaAs and [AIGa]As have been obtained. The data suggest that for irradiation perpendicular to the substrate a competition exists between desorption and photodeposition, which adversely affects film stoichiometry under the conditions studied.