Stephen J. Eglash

High-power GaInAsSb-AlGaAsSb multiple-quantum-well diode lasers emitting at 1.9 /spl mu/m

High-power diode lasers emitting at /spl sim/1.9 /spl mu/m have been fabricated from a quantum-well heterostructure having an active region consisting of five GaInAsSb wells and six AlGaAsSb barriers. For devices 300 /spl mu/m wide and 1000 /spl mu/m long, single-ended output power as high as 1.3 W cw has been obtained with an initial differential quantum efficiency of 47%. The pulsed threshold current density is as low as 143 A/cm/sup 2/ for 2000-/spl mu/m-long devices.<<ETX>>

Double‐heterostructure diode lasers emitting at 3 μm with a metastable GaInAsSb active layer and AlGaAsSb cladding layers

Double‐heterostructure diode lasers emitting at 3 μm have exhibited pulsed operation at temperatures up to 255 K and cw operation up to 170 K, with cw output power of 45 mW/facet at 100 K. The laser structure, grown on GaSb substrates by molecular beam epitaxy, has a metastable GaInAsSb active layer and AlGaAsSb cladding layers. The lowest pulsed threshold current density is 9 A/cm2 obtained at 40 K. The characteristic temperature is 35 K at low temperatures and 28 K above 120 K.

Development and confirmation of the unified model for Schottky barrier formation and MOS interface states on III-V compounds ☆

The object of the work reported here was to develop an understanding on an atomic basis of the interactions between semiconductors and metal or oxygen overlayers which determine the electronic characteristics of the interface, e.g. the Schottky barrier heights and the density and the energy position of states at oxide-semiconductor interfaces. The principal experimental tool used by ourselves was photoemission excited by monochromatized synchrotron radiation (10 eV<hv<300 eV). Extreme surface sensitivity is obtained by tuning the synchrotron radiation so that the minimum escape depth is obtained for the excited electrons of interest. In this way only the last two or three atomic layers of the solid are sampled. By changing hv, core levels or valence bands can be studied. The Fermi level position Efs at the surface can be directly determined using a metallic reference. GaAs, InP and GaSb were studied. On a properly cleaved surface there are no surface states in the semiconductor band gap—thus, no pinning of Efs. Pinning of Efs can then be monitored as metal or oxygen is added to the surface, starting from submonolayer quantities. Two striking results are obtained: (1) the pinning position is independent of the adatom, whether it is oxygen or one of a wide range of metals, and (2) the pinning is completed by much less than a monolayer of adatoms. These results cannot rationally be explained by the hypothesis that the pinning is due to the levels produced directly by the adatoms. Rather, they suggest strongly that the adatoms disturb the semiconductor surface indirectly, forming defect levels. This is supported by the appearance of the semiconductor atoms in the metal and by the disordering of the semiconductor surface by submonolayer quantities of oxygen. Since these basic experiments have been reported previously they are only briefly reviewed here. When metal or oxygen is added under very gentle conditions, the following levels are formed (all energies are relative to the conduction band minimum). Semiconductor Acceptor Donor GaAs 0.65 eV 0.85 eV InP 0.45 eV 0.1 eV GaSb 0.5 eV Below VBM Full-size table Table options View in workspace Download as CSV where VBM denotes the valence band maximum.

Engineered Schottky barrier diodes for the modification and control of Schottky barrier heights

A technique for fabricating controlled Schottky barrier heights to GaAs over the entire band gap is demonstrated. Thin, highly doped semiconductor layers at the metal‐semiconductor interface allowed the reproducible control of the effective barrier height on n‐type GaAs from near zero (i.e., ohmic behavior at 300 K) to 1.33 eV (the band gap equals 1.43 eV at 300 K) with diode ideality factors 1.02≤n≤1.21. Molecular‐beam epitaxy was used to grow GaAs epitaxial layers with in situ deposited Al metal layers, resulting in diodes with nearly ideal electrical and structural characteristics. Electrical characterization by current‐voltage (I‐V) and capacitance‐voltage (C‐V) techniques, models for these I‐V and C‐V characteristics, and structural characterization by high resolution transmission electron microscopy lattice images are presented. Implications of this work for models of Schottky barrier formation are discussed, as well as some applications for these ‘‘engineered Schottky barrier diodes.’’

High‐power diode‐laser‐pumped InAsSb/GaSb and GaInAsSb/GaSb lasers emitting from 3 to 4 μm

Diode‐array‐pumped GaInAsSb/GaSb and InAsSb/GaSb double heterostructure lasers operated at 85 K yielded 95 mW average and 1.5 W peak power per facet at 3 μm, and 50 mW average and 0.8 W peak power facet at 4 μm. The highest operational temperature was 210 K for the 3‐μm quaternary and 150 K for the 4‐μm ternary.

High-efficiency high-power GaInAsSb-AlGaAsSb double-heterostructure lasers emitting at 2.3 mu m

Double-heterostructure Ga/sub 0.84/In/sub 0.16/As/sub 0.14/Sb/sub 0.86/-Al/sub 0.5/Ga/sub 0.5/As/sub 0.04/Sb/sub 0.96/ diode lasers emitting at 2.27 mu m were grown by molecular beam epitaxy on GaSb substrates. For pulsed operation of broad-stripe lasers 300 mu m wide, differential quantum efficiencies as high as 50% and output power as high as 900 mW/facet were obtained for a cavity length of 300 mu m. Values of approximately 100% for the internal quantum efficiency and 43 cm/sup -1/ for the internal loss coefficient were determined from the measured dependence of differential quantum efficiency on cavity length. The threshold current density was as low as 1.5 kA/cm/sup 2/ for a cavity length of 700 mu m. >

InAsSb/AlAsSb double‐heterostructure diode lasers emitting at 4 μm

Double‐heterostructure InAsSb/AlAsSb diode lasers emitting at 4 μm have been fabricated. The laser structure was grown on GaSb substrates by molecular beam epitaxy. The devices exhibit continuous wave operation at temperatures up to 80 K, and pulsed operation up to 155 K. The lowest threshold current density is 33 A/cm2 obtained at 50 K, but the characteristic temperature is only 17 K.

MBE growth of GaInAsSb/AlGaAsSb double heterostructures for infrared diode lasers

Abstract For the fabrication of diode lasers emitting near 2.3 μm, molecular beam epitaxy has been used to grow double heterostructures consisting of a Ga 0.84 In 0.16 As 0.14 Sb 0.86 active layer and Al 0.50 Ga 0.50 As 0.04 Sb 0.96 confining layers lattice matched to a GaSb substrate. Because the sticking coefficient is much greater for Sb than for As, high concentrations of Sb can be incorporated into the alloy layers even though the As flux during growth is much greater than both the Sb flux and the total group III flux. The n- and p-type dopant sources were GaTe and Be, respectively. The lasers have threshold current densities as low as 1.5 kA cm −2 , differential quantum efficiencies as high as 50%, and pulsed output power as high as 900 mW per facet.

Single‐frequency GaInAsSb/AlGaAsSb quantum‐well ridge‐waveguide lasers emitting at 2.1 μm

Ridge‐waveguide lasers emitting at ∼2.1 μm have been fabricated from a GaInAsSb/AlGaAsSb quantum‐well heterostructure grown on a GaSb substrate by molecular beam epitaxy. The cw threshold current is as low as 29 mA at room temperature, and the maximum cw output power is 28 mW. The lasers operate in a single longitudinal mode which can be continuously tuned without mode hopping over 1.2 nm by changing the heatsink temperature and over 0.8 nm by changing the current.

Annealing of intimate Au‐GaAs Schottky barriers: Thick and ultrathin metal films

Using valence‐band and core‐level photoemission spectroscopy (PES) and electrical device measurements, the effects of annealing on Au:n‐type (110) GaAs Schottky diodes fabricated in ultrahigh vacuum have been studied. Similiar trends in the annealing‐induced changes in the barrier height of Au:n‐type GaAs were found for 0.2 and 15 monolayer coverages as determined by PES and for thick film coverages (1000 A) as determined by current‐voltage (I‐V) and capacitance‐voltage (C‐V) measurement techniques. In each case, the barrier height was found to be stable for temperatures between 30 and 200 °C and between 300 and 500 °C; while a gradual decrease in the barrier height was found for annealing temperatures of 200–300 °C. These changes are correlated with the formation of a Au‐Ga rich layer at the interface during anneals at 200 to 300 °C. Leakage currents were found to dominate the I‐V characteristics in the devices which were annealed above the Au‐Ga eutectic temperature. These peripheral leakage currents we...