M. J. Pullin

Type-II InAs/InAsSb strained-layer-superlattice negative luminescence devices

Negative luminescence operation is reported for p–n diode devices with type-II InAs/InAsSb strained-layer-superlattice active regions which have a spectral peak at 4.2 μm and a negative luminescence efficiency of up to 20%.

SUPPRESSION OF AUGER RECOMBINATION IN ARSENIC-RICH INAS1-XSBX STRAINED LAYER SUPERLATTICES

Room-temperature pump-probe transmission experiments have been performed on an arsenic-rich InAs/InAs1-xSbx strained layer superlattice (SLS) above the fundamental absorption edge near 10 mu m, using a ps far-infrared free-electron laser. Measurements show complete bleaching at the excitation frequency, with recovery times which are found to be strongly dependent on the pump photon energy. At high excited carrier densities, corresponding to high photon energy and interband absorption coefficient, the recombination is dominated by Auger processes, A direct comparison with identical measurements on epilayers of InSb, of comparable room-temperature band gap, shows that the Auger processes have been substantially suppressed in the superlattice case as a result of both the quantum confinement and strain splittings in the SLS structure, In the nondegenerate regime, where the Auger lifetime scales as tau(aug)(-1)=C1Ne2, a value of C-1 some 100 times smaller is obtained for the SLS structure. The results have been interpreted in terms of an 8x8 k . p SLS energy band calculation, including the full dispersion for both k in plane and k parallel to the growth direction. This is the strongest example of room-temperature Auger suppression observed to date for these long-wavelength SLS alloy compositions and implies that these SLS materials may be attractive for applications as room-temperature mid-IR diode lasers

4-11 Mu-M Infrared-Emission and 300 K Light-Emitting-Diodes From Arsenic-Rich Inas1-Xsbx Strained-Layer Superlattices

Arsenic-rich InAs/lnAs1-xSbx strained layer superlattices (SLSs) grown on GaAs substrates by molecular beam epitaxy (MBE) are studied for their potential application as infrared emitters. The long-wavelength emission (4-11 mu m) is highly sensitive to superlattice design parameters and is accounted for by a large type-II band offset, greater than in previously studied antimony-rich InSb/lnAs1-xSbx SLSs. High internal PL efficiencies (>10%) and intense luminescence emission were observed at these long wavelengths despite large dislocation densities. Initial unoptimized InAs/lnAs1-xSbx SLS light emitting diodes gave approximately=200 nW of lambda =5 mu m emission at 300 K.

Room-temperature InAsSb strained-layer superlattice light-emitting diodes at λ=4.2 μm with AlSb barriers for improved carrier confinement

Room-temperature InAs/InAs1−xSbx strained-layer superlattice light-emitting diodes (x∼8%) are reported that emit at λ∼4.2 μm with an internal efficiency of 2.8%. The structures are grown by molecular beam epitaxy on slightly mismatched InAs substrates and include a strained AlSb barrier layer to prevent electron migration to the dislocated substrate–epilayer interface region. Comparison with a near identical structure grown without the barrier layer indicates a factor of four improvement in device efficiency at room temperature.

Efficient 300 K light-emitting diodes at λ∼5 and ∼8 μm from InAs/In(As1−xSbx) single quantum wells

300 K light-emitting diodes which emit at 5 and 8 μm with quasi-cw output powers of up to 50 and 24 μW, respectively, are reported. The devices have a single molecular beam epitaxy grown InAs/In(As, Sb) quantum well in the active region with a strong type-IIa band alignment giving mid-IR emission at energies up to 64% lower than the alloy band gap. The emission energies are shown to be in good agreement with a k⋅p bandstructure model where Qc, the ratio of the strained conduction-band offset to the band-gap difference between the two strained superlattice components, is found to be ∼2.0.

A MAGNETO-PHOTOLUMINESCENCE INVESTIGATION OF THE BAND OFFSET BETWEEN INAS AND ARSENIC-RICH INAS1-XSBX ALLOYS

InAs/InAs0.865Sb0.135 quantum wells are characterized using magneto‐photoluminescence. Band‐ to‐band transitions are found at energies lower than the band gaps of either the InAs or the InAs0.865Sb0.135 with photoluminescence emission at wavelengths up to 4.8 μm. By modeling the quantum size shifts of the photoluminescence transitions and their energy shift in a magnetic field, the valence band offset between InAs and In(As,Sb) is deduced to be type II with electron confinement in the In(As,Sb) alloy and hole confinement in InAs.

Improved-efficiency positive and negative luminescent light-emitting devices for mid-infrared gas-sensing applications

InAs/InAsSb SQW LEDs incorporating AlAs0.02Sb0.98 or In0.83Al0.17As electron confining barrier layers are reported. Devices emitting 108 (mu) W and 84 (mu) W at 300 K with QW emission at (lambda) equals 4.1 micrometer and (lambda) equals 4.7 micrometer exhibit quantum efficiencies that are improved by factors of 7 and 3.4 respectively over control samples without the barrier. The operating wavelength of negative luminescent (NL) devices with InAs/In(As,Sb) strained-layer-superlattice (SLS) active regions has been extended to (lambda) equals 6.8 micrometer. NL performance is limited by leakage currents that originate in the n+ contact layer.

Optical studies of InAs/In(As,Sb) single quantum well (SQW) and strained-layer superlattice (SLS) LEDs for the mid-infrared (MIR) region

We report on electroluminescence and photoluminescence studies of arsenic rich InAs1-xSbx heterostructure LEDs for the MIR region. Single-quantum- well LEDs have demonstrated 300 K of approximately 24 (mu) W and approximately 50 (mu) W and approximately 8 micrometers , respectively, with corresponding internal quantum efficiencies of 0.8% and 1.6%. We also demonstrate 4.2 micrometers , 300 K emission from strained-layer superlattice (SLS) LEDs with AlSb electron confining barriers with output powers > 0.1 mW. In reverse bias, these SLS devices exhibit negative luminescence efficiencies of approximately 14% at 310 K.

The evaluation and control of quantum wells and superlattices of III–V narrow gap semiconductors

The growth and evaluation of InAs/GaSb/AlSb quantum wells and InAs, -,Sb,/InAs strained layer superlattices are discussed. A characteristic of the InAs/GaSb/AISb combinations is their high mobility and the applications are mainly concerned with optimising the mobility. The InAs, _ ,

Photoluminescence studies of n-i-p-i superlattices in InSb and InAs: suppression of Auger recombination due to type II potentials

b,/InAs strained-layer superlattices have rather long non-radiative lifetimes despite inferior structural quaIity, as demonstrated by time-resolved pump-probe measurements with a free electron laser. Q 1997 Published by Elsevier Science S.A.