We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other.

Band parameters for III–V compound semiconductors and their alloys

This letter presents a type of infrared detector named the nBn detector. The nBn design essentially eliminates Shockley-Read-Hall generation currents. The result is greatly reduced dark current and noise, compared to other midwave infrared detectors, such as p-n photodiodes. This enables the nBn to operate at background-limited infrared photodetection conditions at significantly higher temperatures than conventional midwave infrared detectors and have greater detectivity near room temperature. The nBn is demonstrated in InAs and InAsSb materials, exhibiting cutoff wavelengths of 3.4 and 4.2μm, respectively.

nBn detector, an infrared detector with reduced dark current and higher operating temperature

The initial stages of GaAs overgrowth over self-assembled coherently strained InAs quantum dots (QDs) are studied. For small GaAs coverages (below 5 nm), atomic force microscopy (AFM) images show partially covered island structures with a regular size distribution which are elongated in the [011] direction. Analysis of the AFM profiles show that a large anisotropic redistribution of the island material is taking place during the initial GaAs overgrowth. Short time annealing experiments together with photoluminescence spectroscopy on annealed QDs are consistent with a Ga and In intermixing during the overgrowth. Surface QDs capped with 5 nm or more GaAs show a strong luminescence intensity indicating that surface QDs are remarkably insensitive to surface recombination effects.

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Intermixing and shape changes during the formation of InAs self-assembled quantum dots

Undoped AlGaN/GaN structures are used to fabricate high electron mobility transistors (HEMTs). Using the strong spontaneous and piezoelectric polarization inherent in this crystal structure a two-dimensional electron gas (2DEG) is induced. Three-dimensional (3-D) nonlinear thermal simulations are made to determine the temperature rise from heat dissipation in various geometries. Epitaxial growth by MBE and OMVPE are described, reaching electron mobilities of 1500 and 1700 cm/sup 2//Ns, respectively, For electron sheet density near 1/spl times/10/sup 13//cm/sup 2/, Device fabrication is described, including surface passivation used to sharply reduce the problematic current slump (dc to rf dispersion) in these HEMTs. The frequency response, reaching an intrinsic f/sub t/ of 106 GHz for 0.15 /spl mu/m gates, and drain-source breakdown voltage dependence on gate length are presented. Small periphery devices on sapphire substrates have normalized microwave output power of /spl sim/4 W/mm, while large periphery devices have /spl sim/2 W/mm, both thermally limited. Performance, without and with Si/sub 3/N/sub 4/ passivation are presented. On SiC substrates, large periphery devices have electrical limits of 4 W/mm, due in part to the limited development of the substrates.

Undoped AlGaN/GaN HEMTs for microwave power amplification

Monte Carlo simulations of electron transport based upon an analytical representation of the lowest conduction bands of bulk, wurtzite phase GaN are used to develop a set of transport parameters for devices with electron conduction in GaN. Analytic expressions for spherical, nonparabolic conduction band valleys at the Γ, U, M, and K symmetry points of the Brillouin zone are matched to experimental effective mass data and to a pseudopotential band structure. The low-field electron drift mobility is calculated for temperatures in the range of 300–600 K and for ionized impurity concentrations between 1016 and 1018 cm−3. Compensation effects on the mobility are also examined. Electron drift velocities for fields up to 500 kV/cm are calculated for the above temperature range. To aid GaN device modeling, the drift mobility dependences on ambient temperature, donor concentration, and compensation ratio are expressed in analytic form with parameters determined from the Monte Carlo results. Analytic forms are also...

Electron transport characteristics of GaN for high temperature device modeling

Local high current densities in areas around dislocations with a screw component might be responsible for the observed high leakage currents in GaN-based electronic devices. Using ballistic electron emission microscopy, threading dislocations with a screw component are found to be accompanied by high current densities and low effective Schottky barrier heights. The electronic states responsible for this extremely nonuniform behavior of GaN films are metastable trap states. The experimental results show that acceptor- and donor-like charge traps coexist in the vicinity of dislocations with a screw component.

Direct observation of localized high current densities in GaN films

Single InAs self-assembled quantum dots buried spatially beneath a Au/GaAs interface are probed for the first time using the imaging and spectroscopic modes of ballistic electron emission microscopy (BEEM). BEEM images show enhanced current through each dot. Spectra taken with the tip positioned on a dot show shifted current thresholds when compared with the off dot spectra, which are essentially the same as those of Au on bulk GaAs. Shifts in the $\ensuremath{\gamma}$ and $L$ conduction band thresholds are attributed to strain in the GaAs cap layer. Fine structure below the $\ensuremath{\gamma}$ threshold is consistent with resonant tunneling through zero-dimensional states within the quantum dots.

Imaging and Spectroscopy of Single InAs Self-Assembled Quantum Dots using Ballistic Electron Emission Microscopy.

Ballistic electron emission microscopy (BEEM) has been used to study transport in a double barrier resonant tunneling structure. Unlike conventional transport techniques, BEEM allows the injected electron energy to be varied independent of the band profile. We report the observation of quasi-bound states and band-structure effects as deduced from the temperature evolution of the BEEM spectra. The BEEM thresholds are found to be in good agreement with the calculated energetically favorable levels. Our results show that BEEM is a powerful spectroscopic tool for studying quantum structures.

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Direct Observation of Quasi-Bound States and Band-Structure Effects in a Double Barrier Resonant Tunneling Structure Using Ballistic Electron Emission Microscopy.

Ballistic electron emission microscopy (BEEM) measurements on GaN grown on sapphire substrates reveal a second conduction band minimum ∼340 meV above the absolute band minimum at the zone center (Γ point). A significant lateral variation of the energy difference between the two band minima, ±50 meV, was observed which may result from nonuniform strain in the material. The existence of two conduction bands in close proximity may affect device applications, i.e., GaN based lasers and electronic devices.

Ballistic electron emission microscopy study of transport in GaN thin films

GaSb self-assembled quantum dots grown by molecular beam epitaxy on GaAs exhibit a staggered (type II) band lineup with a potential barrier in the conduction band. Traditional methods cannot measure this local band offset because of the small (∼50 nm) lateral dot size. The nanometer resolution of ballistic electron emission microscopy is exploited to image individual dots and measure a local band offset of 0.08±0.02 eV.

M. A. Chin

Papers

Direct observation of localized high current densities in GaN films

Imaging and Spectroscopy of Single InAs Self-Assembled Quantum Dots using Ballistic Electron Emission Microscopy.

Direct Observation of Quasi-Bound States and Band-Structure Effects in a Double Barrier Resonant Tunneling Structure Using Ballistic Electron Emission Microscopy.

Ballistic electron emission microscopy study of transport in GaN thin films

Local conduction band offset of GaSb self-assembled quantum dots on GaAs