J. R. Meyer

Band parameters for nitrogen-containing semiconductors

We present a comprehensive and up-to-date compilation of band parameters for all of the nitrogen-containing III–V semiconductors that have been investigated to date. The two main classes are: (1) “conventional” nitrides (wurtzite and zinc-blende GaN, InN, and AlN, along with their alloys) and (2) “dilute” nitrides (zinc-blende ternaries and quaternaries in which a relatively small fraction of N is added to a host III–V material, e.g., GaAsN and GaInAsN). As in our more general review of III–V semiconductor band parameters [I. Vurgaftman et al., J. Appl. Phys. 89, 5815 (2001)], complete and consistent parameter sets are recommended on the basis of a thorough and critical review of the existing literature. We tabulate the direct and indirect energy gaps, spin-orbit and crystal-field splittings, alloy bowing parameters, electron and hole effective masses, deformation potentials, elastic constants, piezoelectric and spontaneous polarization coefficients, as well as heterostructure band offsets. Temperature an...

Auger lifetime enhancement in InAs–Ga1−xInxSb superlattices

We have experimentally and theoretically investigated the Auger recombination lifetime in InAs–Ga1−xInxSb superlattices. Data were obtained by analyzing the steady‐state photoconductive response to frequency‐doubled CO2 radiation, at intensities varying by over four orders of magnitude. Theoretical Auger rates were derived, based on a k⋅p calculation of the superlattice band structure in a model which employs no adjustable parameters. At 77 K, both experiment and theory yield Auger lifetimes which are approximately two orders of magnitude longer than those in Hg1−xCdxTe with the same energy gap. This finding has highly favorable implications for the application of InAs–Ga1−xInxSb superlattices to infrared detector and nonlinear optical devices.

Rebalancing of internally generated carriers for mid-infrared interband cascade lasers with very low power consumption

The interband cascade laser differs from any other class of semiconductor laser, conventional or cascaded, in that most of the carriers producing population inversion are generated internally, at semimetallic interfaces within each stage of the active region. Here we present simulations demonstrating that all previous interband cascade laser performance has suffered from a significant imbalance of electron and hole densities in the active wells. We further confirm experimentally that correcting this imbalance with relatively heavy n-type doping in the electron injectors substantially reduces the threshold current and power densities relative to all earlier devices. At room temperature, the redesigned devices require nearly two orders of magnitude less input power to operate in continuous-wave mode than the quantum cascade laser. The interband cascade laser is consequently the most attractive option for gas sensing and other spectroscopic applications requiring low output power and minimum heat dissipation at wavelengths extending from 3 μm to beyond 6 μm.

Graded band gap for dark-current suppression in long- wave infrared W-structured type-II superlattice photodiodes

A new W-structured type-II superlattice photodiode design, with graded band gap in the depletion region, is shown to strongly suppress dark currents due to tunneling and generation-recombination processes. The long-wave infrared (LWIR) devices display 19%–29% quantum efficiency and substantially reduced dark currents. The median dynamic impedance-area product of 216Ωcm2 for 33 devices with 10.5μm cutoff at 78K is comparable to that for state-of-the-art HgCdTe-based photodiodes. The sidewall resistivity of ≈70kΩcm for untreated mesas is also considerably higher than previous reports for passivated or unpassivated type-II LWIR photodiodes, apparently indicating self-passivation by the graded band gap.

Continuous-wave operation of λ=3.25 μm broadened-waveguide W quantum-well diode lasers up to T=195 K

Mid-infrared (λ=3.25 μm) broadened-waveguide diode lasers with active regions consisting of 5 type-II “W” quantum wells operated in continuous-wave (cw) mode up to 195 K. At 78 K, the threshold current density was 63 A/cm2, and up to 140 mW of cw output power was generated. A second structure with ten quantum wells operated up to 310 K in pulsed mode.

Interband cascade laser emitting at λ=3.75μm in continuous wave above room temperature

We report a five-stage interband cascade laser that operates at λ=3.75μm in cw mode up to a maximum temperature of 319K. With gold electroplating, epitaxial-side-up mounting, and one facet coated for high reflectivity, a 3mm×9.2μm ridge emits over 10mW of cw power at 300K.

Auger coefficients in type-II InAs/Ga1−xInxSb quantum wells

Two different approaches, a photoconductive response technique and a correlation of lasing thresholds with theoretical threshold carrier concentrations have been used to determine Auger lifetimes in InAs/GaInSb quantum wells. For energy gaps corresponding to 3.1–4.8 μm, the room-temperature Auger coefficients for seven different samples are found to be nearly an order-of-magnitude lower than typical type-I results for the same wavelength. The data imply that at this temperature, the Auger rate is relatively insensitive to details of the band structure.

Improved quantitative mobility spectrum analysis for Hall characterization

We present an improved quantitative mobility spectrum analysis (i-QMSA) procedure for determining free electron and hole densities and mobilities from magnetic-field-dependent Hall and resistivity measurements on bulk or layered semiconductor samples. The i-QMSA technique is based on a fundamentally new approach, which optimizes the fit to the conductivity tensor components and their slopes by making those adjustments in the mobility spectra that result in the greatest error reduction. Empirical procedures for manipulating the mobility spectra are also introduced, with the dual purpose of reducing the error of the fit and simplifying the shape of the spectra to minimize the presence of unphysical artifacts. A fully automated computer implementation of the improved QMSA is applied to representative synthetic and real data sets involving various semiconductor material systems. These results show that, as compared with previous approaches, the presented algorithm maximizes the information that may be extract...

W-structured type-II superlattice long-wave infrared photodiodes with high quantum efficiency

Results are presented for an enhanced type-II W-structured superlattice (WSL) photodiode with an 11.3μm cutoff and 34% external quantum efficiency (at 8.6μm) operating at 80K. The new WSL design employs quaternary Al0.4Ga0.49In0.11Sb barrier layers to improve collection efficiency by increasing minority-carrier mobility. By fitting the quantum efficiencies of a series of p-i-n WSL photodiodes with background-doped i-region thicknesses varying from 1to4μm, the authors determine that the minority-carrier electron diffusion length is 3.5μm. The structures were grown on semitransparent n-GaSb substrates that contributed a 35%–55% gain in quantum efficiency from multiple internal reflections.

High-temperature continuous-wave 3–6.1 μm “W” lasers with diamond-pressure-bond heat sinking

Optically pumped type-II W lasers emitting in the mid-infrared exhibited continuous-wave (cw) operating temperatures of 290 K at λ=3.0 μm and 210 K at λ=6.1 μm. Maximum cw output powers for 78 K were 260 mW at λ=3.1 μm and nearly 50 mW at λ=5.4 μm. These high maximum temperatures were achieved through the use of a diamond-pressure-bonding technique for heat sinking the semiconductor lasers. The thermal bond, which is accomplished through pressure alone, permits topside optical pumping through the diamond at wavelengths that would be absorbed by the substrate.