R. M. Biefeld

The effect of H2 on morphology evolution during GaN metalorganic chemical vapor deposition

In situ optical reflectance transients reveal that the morphology evolution of the initial low-temperature buffer layer strongly influences the structural and electrical quality of the high-temperature GaN films. Moreover, the morphology evolution of that buffer layer, specifically evolution of the spatial and orientational distributions of the nuclei, is strongly affected by H2. The growth conditions for which surface smoothness is maintained throughout the two-step growth do not necessarily produce the best quality final GaN films; instead, there may be an optimal roughness and incubation period en route to the best quality final films.

The band-gap bowing of AlxGa1−xN alloys

The band gap of AlxGa1−xN is measured for the composition range 0⩽x 800 °C usually lead to stronger apparent bowing (b>+1.3 eV); while growths initiated using low-temperature buffers on sapphire, followed by high-temperature growth, lead to weaker bowing (b<+1.3 eV). Extant data suggest that the intrinsic band-gap bowing parameter for AlGaN alloys is b=+0.62(±0.45) eV.

A GaAsxP1−x/GaP strained‐layer superlattice

Strained−layer superlattices form a broad new class of semiconductor materials with tailorable electronic properties. We have succeeded in growing a GaAsxP1−x/GaP(100) strained−layer superlattice (SLS). The structure was grown by alternate metalorganic chemical vapor deposition of thin (60 A)layers (20 each) of GaAs0.4P0.6 and GaP. These layers were grown onto a GaAsxP1−x layer which was graded in composition from x = 0 (composition of underlying GaP substrate)to x = 0 (average composition of the SLS). Photoluminescense studies of the SLS were carried out to determine the optical band gap. At T = 78 K, the spectrum shows a dominant band−edge peak at 2.03 eV as well as weaker peaks at higher energies. Tight binding and effective mass calculations, also carried out, predict a direct band gap (due to zone folding) of 2.02 eV and higher lying transition energies which are in good agreement with these data.

The metal-organic chemical vapor deposition and properties of III–V antimony-based semiconductor materials

Abstract This article comprehensively reviews the growth of III–V antimony-based semiconductor materials using metal-organic chemical vapor deposition (MOCVD). It does this by first discussing the general trends found for the growth of these materials. Next the specific growth techniques are discussed for each of the antimony-based systems including the binaries InSb, GaSb, and AlSb. The growth techniques used for many of the ternaries and quaternaries of these materials are also discussed. Following this a brief description of the use of dopants, novel organometallic sources and superlattices is presented. Next, the use of common characterization techniques is presented for different types of materials. A variety of the types of devices is then presented followed by a short summary and forecast of future directions that are currently being pursued in these materials.

InAsSb‐based mid‐infrared lasers (3.8–3.9 μm) and light‐emitting diodes with AlAsSb claddings and semimetal electron injection, grown by metalorganic chemical vapor deposition

Gain‐guided, injection lasers using AlAsSb for optical confinement and a strained InAsSb/InAs multiquantum well active region were grown by metalorganic chemical vapor deposition. The semi‐metal properties of a p‐GaAsSb/n‐InAs heterojunction are utilized as a source for injection of electrons into the active region of the laser. In pulsed mode, the laser operated up to 210 K with an emission wavelength of 3.8–3.9 μm. We also report on the two‐color emission of a light‐emitting diode with two different active regions to demonstrate multistage operation of these ‘‘unipolar ’’ devices.

The preparation of InSb and InAs1−x Sbx by metalorganic chemical vapor deposition

Abstract Epitaxial layers of the compound semiconductors InSb and InAs 1− x Sb x have been prepared by metal organic chemical vapor deposition in a vertical, atmospheric pressure quartz reactor. Trimethylindium (TMI), trimethylantimony (TMSb) and arsine diluted in H 2 were used as the In, Sb and As sources. A temperature range of 400 to 550°C and molar gas phase flow ratios of TMI to the flow of AsH 3 + TMSb of 0.08 to 1.2 were investigated. For 0.05 x ⩽ 1.0 the best surface morphologies were obtained for growth rates

Midwave (4 μm) infrared lasers and light‐emitting diodes with biaxially compressed InAsSb active regions

Heterostructures with biaxially compressed, As‐rich InAsSb are being investigated as active regions for midwave infrared emitters. InAs1−xSbx/In1−xGaxAs (x≊0.1) strained‐layer sublattices (SLSs), nominally lattice matched to InAs, were grown using metalorganic chemical vapor deposition. An SLS light‐emitting diode was demonstrated which emitted at 3.6 μm with 0.06% efficiency at 77 K. Optically pumped laser emission at 3.9 μm was observed in a SLS/InPSb heterostructure. The laser had a maximum operating temperature of approximately 100 K.

Stability of strained quantum-well field-effect transistor structures

Conditions for stability of strained-layer structures and their implications for device fabrication are examined. Structures which have exhibited the best performance to date are found to be thermodynamically metastable (or at best marginally stable) structures, which will restrict the processing steps permissible in the integration of these devices to form complex circuits.<<ETX>>

OMVPE growth and gas-phase reactions of AlGaN for UV emitters

Gas-phase parasitic reactions among TMG, TMA, and NH3, are investigated by monitoring of the growth rate/incorporation efficiency of GaN and AlN using an in-situ optical reflectometer. It is suggested that gas phase adduct (TMA: NH{sub 3}) reactions not only reduce the incorporation efficiency of TMA but also affect the incorporation behavior of TMGa. The observed phenomena can be explained by either a synergistic gas-phase scavenging effect or a surface site-blocking effect. Relatively low reactor pressures (30--50 Torr) are employed to grow an AlGaN/GaN QW p-n diode structure. The UV emission at 354 nm (FWHM {approximately} 6 nm) represents the first report of LED operation from an indium-free GaN QW diode.

Extended infrared response of InAsSb strained-layer superlattices

Strained‐layer superlattices of InAsSb were grown with low densities of dislocations and microcracks for optical characterization to determine the suitability of these structures for infrared photodetectors. Infrared transmission measurements revealed absorption throughout the 8–12 μm region and extended to longer wavelengths than predicted from consideration of the tensile strain‐induced band‐gap shift in a type‐I superlattice. We conclude that a type‐II superlattice occurs in the InAsSb system for alloy compositions >60% Sb.