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Electron mobility of two-dimensional electron gas (2-DEG) at the AlGaN/GaN interface is investigated and reported.

A new simulation approach to obtain diffusion-controlled atomic concentration profiles in II-VI semiconductor heterostructures has been developed using x-ray diffraction. Simulations based on direct summation of scattered waves across the heterostructure was compared with measured diffraction spectra. The diffusion profiles obtained from the x-ray diffraction spectra were compared with secondary-ions mass spectrometry results, and the advantages of the new approach are discussed.

A simple one-dimensional model helps elucidate the electrical and optical performances of linearly graded n-type HgCdTe heterojunction photodiodes. Solutions to the continuity equation for the spatial dependency of band gap, absorption coefficient and intrinsic carrier concentration enable the examination of the influence of electric fields on the figures of merit of the diodes. The electric fields decrease the influence of the defective CdTe HgCdTe interface present at the backside.

Analysis of the data from HgCdTe heterojunction photodiode experiments reveals that light illumination through the opaque n-type layer and transparent P-layer of photodiodes results in high quantum efficiency, which is independent of various diode characteristics. Variations in band gap, and the presence of a built-in electric field in the n-layer results in the absorption and collection of photons through drift and diffusion processes by the n-layer. Solutions to the one-dimensional continuity equation in the linearly graded n-type area help compute the quantum efficiency and confirm that built-in electric field elevates the diode performance.

Study of the vertical drift mobility of excited carriers in a multi quantum well structure revealed the influence of detector performance on internal scattering of hot electrons. Photogeometrical magnetoresistance techniques facilitated the extraction of low temperature mobility.

The effect of illumination direction and geometry on the quantum efficiency of HgCdTe photodiodes was investigated. The results showed that quantum efficiency was dependent on the manner in which light was introduced. The structure in which light was absorbed following its crossing of the transparent region is correlated with higher quantum efficiency and homogeneity. The width of the absoroption region had no effect on the quantum efficiency of absorption region widths higher than a certain minimum.

In-plane photoconductivity (PC) measurements in a GaN/AlN quantum dots (QDs) layer show a TM-polarized infrared (IR) peak, at 0.9 eV, and a visible-UV (vis-UV) peak, at 2.8 eV. Based on the energy and polarization dependence, the 0.9 eV is associated with the polarized S to Pz intraband transition within the QDs. The IR PC turns from positive PC (PPC) to negative PC (NPC) as temperature is raised, increasing exponentially from 50 to 300 K. Vis-UV radiation renders PPC at all temperatures. Combined with vis-UV radiation, the IR PC is negative even at low temperatures. Based on these observations, we suggest a model in which IR excited carriers in the QD layer are coupled to deep levels (DLs) in the AlN barrier and turn immobile, i.e., NPC is observed. Vis-UV radiation re-excites them into the QDs, resulting in PPC. At lower temperatures coupling into the DL becomes inefficient, thus, IR excitation results in PPC. This model was translated into rate equations. Simulations based on these rate equations reproduce well the experimental results. [ABSTRACT FROM AUTHOR]

GaN/AlN quantum dots (QDs) grown on sapphire/GaN substrate have been realized by low-pressure metalorganic chemical vapor deposition. The influence of the growth conditions, postgrowth annealing ambience, and roughness of AlN template surface has been investigated. QDs with 3–10 nm height, 40–100 nm diameter, and density from 1×1011 down to 1×108 cm-2 were achieved by adjusting the growth temperature, V/III ratio, and growth time. For the formation of QDs, the postgrowth annealing in H2 is more favorable than that in NH3; however, it results in a bad surface of wetting layer and therefore is not suitable for device fabrication. When rough-surface templates were used, small-sized dots with the same density as obtained on smooth-surface templates could be found besides some large clusters. An intense photoluminescence peak of QDs is observed at 15 K and up to room temperature. [ABSTRACT FROM AUTHOR]

A reduced model is developed that has significant advantages over the full drift-diffusion model for the simulation of laser beam-induced current (LBIC) signals in the presence of heterojunctions. The model determines the contribution to the LBIC signal that would occur from photogeneration at any position within the semiconductor, and is particularly useful for heterostructures where judicious choice of illumination wavelength can result in photogeneration at different depths within the device structure. The reduced model is used to examine the basic features of LBIC as applied to two types of planar P-n HgCdTe heterojunction photodiode structures. In particular, the question of correctly identifying erroneous device structures formed during the fabrication process is addressed, and experimental measurements are presented to support the simulation results. [ABSTRACT FROM AUTHOR]

A nonparabolic three-band k.p model enables measurement of the intrinsic carrier concentration and Fermi level of semiconductor materials to provide simple expressions that depend on temperature, semiconductor band gap, carrier effective masses and nonparabolicity factors. The method operates in a temperature range of 0-400k and considers electron contribution in the lowest conduction band, heavy and light holes. This method calculates carrier concentration using an approximation for the nonparabolic Fermi-Dirac integral.

Photoconductive response and optical transmission of P-type quantum well infrared photodetectors exhibit differential polarization dependence. Photoconductive response depends on parallel polarized light and optical transmission reacts more to perpendicularly polarized light. Variations in the vertical transport properties of heavy and light holes and hole subbands account for the difference in polarization dependence.

Presents a study which measured the silicon and iron depth distributions in silicon-implanted semi-insulating indium phosphide as a function of implant temperature and post-implants annealing technique. Applications of indium phosphide in optoelectronic and microwave devices; Investigation of the initial crystalline quality; Redistribution of iron following room temperature implant of silicon and annealing.

Presents a study that investigated the lifetime and carrier-concentration profile of boron-implanted p-type mercury compound photodiodes. Common technique for producing the p-type junctions; Details on the carrier profile measurement; Discussion on the results of the study.

Presents information on a study which demonstrated a comparison between the optical transmission and the photoconductive response of p-type quantum well infrared photodetectors. Background of the study; Methodology of the study; Results and discussion.

Discusses the use of Rutherford backscattering channeling experiments in studying the regrowth of phosphorus or silicon implanted indium phosphorus following thermal annealing. Relation of stoichiometric imbalance to the retardation of implantation; Role of ion implantation for microelectronic and electro-optical devices.