K. C. Baucom

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.

The growth of InP1-xSbx by metalorganic chemical vapor deposition

InP1-xSbx was grown by metalorganic chemical vapor deposition under a variety of conditions. The V/III vapor phase ratio was varied from 327 to 12 over a temperature range of 450–525°C, at pressures of 77 to 660 Torr and growth rates of 0.30 to 2.0 μm/h. For some samples, the V/III vapor phase ratio was optimized for InP1-xSbx lattice matched to InAs to give smooth morphologies and lattice matching with a minimized variation of composition versus changes in the TMSb/(TMSb+PH3) ratio. Examination by transmission electron microscopy indicates that the materials are not single phase, but have undergone a spinodal decomposition, which is consistent with thermodynamic calculations. When our specimen compositions are corrected for strain relaxation, the infrared photoluminescence measurements indicate a lower energy photoluminescence peak for these materials than had been previuosly reported in the literature. Infrared absorption and photoconductivity measurements indicate no sharp band edge as would be expected for a direct gap semiconductor. The observed broad spectra are consistent with alloy decomposition.

Microstructures of InAs 1–x Sb x (x=0.07-0.14) alloys and strained-layer superlattices

Growth of InAs1−xSbx alloys by metalorganic chemical vapor deposition at 475°C results in CuPt ordering even at Sb concentrations as low as x = 0.07-0.14. The two {111}B variants are present, but each exists separately in 1-2 μm regions. However, the ordering is incomplete: it occurs in platelet domains lying on habit planes tilted 30° from (001) within a disordered matrix and is not continuous at the atomic scale within the domains. This ordering apparently explains the reduction in infrared emission energies relative to the bandgaps of bulk alloys. Similar ordering is found in an InAs0.91Sb0.09/In0.g7Ga0.13As strained-layer superlattice with lower-than-expected emission energy. High-resolution images indicate that the superlattice layers flat and regularly spaced. Infrared LEDs have been made from such superlattices.

HIGH SLOPE EFFICIENCY, CASCADED MIDINFRARED LASERS WITH TYPE I INASSB QUANTUM WELLS

Lasers and light-emitting diodes with multistage, type I InAsSb/InAsP quantum well active regions are reported. These ten stage, cascaded devices were grown by metalorganic chemical vapor deposition. The broadband light-emitting diodes produced high average powers, >2 mW (∼80 K, 3.7 μm) and >0.1 mW (∼300 K, 4.3 μm). A 3.8–3.9 μm laser structure operated up to T=180 K. At 80 K, peak power >100 mW and a slope efficiency of 48% (4.8% per stage) were observed in our gain guided lasers. The slope efficiency was strongly dependent on cavity length, and analysis of efficiency data suggests an internal differential quantum efficiency >1 and a loss coefficient ⩾100 cm−1.

The growth of InAs1-xSbx/InAs strained-layer superlattices by metalorganic chemical vapot deposition

InAs{sub 1-x}Sb{sub x}/InAs strained-layer superlattice (SLS) semiconductors and thick epitaxial layers of InAs{sub 1-x}Sb{sub x} were grown under a variety of conditions by metal-organic chemical vapor deposition on InAs substrates. The III/V ratio was varied from 0.026 to 1.0 over a temperature range of 475--525C, at pressures of 200 to 660 torr and growth rates of 0.75 to 3.0 {mu}m/hour. The composition of the ternary can be predicted from the input gas molar flow rates using a thermodynamic model. At lower temperatures, the thermodynamic model must be modified to take account of the incomplete decomposition of arsine and trimethylantimony. These layers were characterized by optical microscopy, SIMS, and x-ray diffraction. The optical properties of these SLS`s were determined by infrared photoluminescence and absorption measurements. The PL peak energies of the alloys` and the SLS`s are consistently lower than the previously reported values for the bandgap of InAs{sub 1-x}Sb{sub x} alloys.

Progress in the growth of mid-infrared InAsSb emitters by metal-organic chemical vapor deposition

The authors report on recent progress and improvements in the metal-organic chemical vapor deposition (MOCVD) of mid-infrared InAsSb emitters using a high speed rotating disk reactor (RDR). The devices contain AlAsSb claddings and strained InAsSb active regions. These emitters have multi-stage, type 1, InAsSb/InAsP quantum well active regions. A semi-metal GaAsSb/InAs layer acts as an internal electron source for the multistage injection lasers and AlAsSb is the electron confinement layer. These structures are the first MOCVD multi-stage devices. Growth in an RDR was necessary to avoid the previously observed Al memory effects found in a horizontal reactor. Broadband LED`s produced 2 mW average power at 3.7 {micro}m and 80 K and 0.1 mW at 4.3 {micro}m and 300 K. a multi-stage, 3.8--3.9 {micro}m laser structure operated up to T = 180 K. At 80 K, peak-power > 100 mW/facet and a high slope efficiency (48%) were observed in these gain guided lasers.

Growth of InSb using tris(dimethylamino)antimony and trimethylindium

We have grown epitaxial layers of InSb on p−‐InSb substrates by metalorganic chemical vapor deposition using tris(dimethylamino)antimony (TDMASb) and trimethylindium (TMIn). Growth temperatures from 285 to 500 °C and pressures from 76 to 660 Torr have been investigated. The V/III ratio was varied from 0.63 to 8.6 using growth rates from 0.06 to 0.67 μm/h. For temperatures ≤425 °C, the growth rate was proportional to the temperature. The growth rate was proportional to the TMIn flow at all temperatures. Temperatures ≳400 °C produced p‐type layers while growth temperatures ≤400 °C produce n‐type layers. The pyrolysis temperature of TDMASb appears to be lower than that of TMIn.

Substrate orientation and surface morphology improvements for InSb grown by metalorganic chemical vapor deposition

Misoriented InSb substrates were used for the growth of InSb with two new organometallic Sb sources, tris(dimethylamino)antimony (TDMASb), and tertiarybutyldimethylantimony (TBDMSb). The surface morphology of InSb grown using either TDMASb or TBDMSb was very rough for growth temperatures ≤ 425°C. This surface roughness is associated with low temperature and excess Sb or high V/III ratios. Smoother surfaces were generally found when using off-axis substrates. The details of the defects observed on the surfaces were dependent on the type of misorientation and can be related to the atomic structure of the surface steps. The smoothest surfaces were obtained for growth on InSb substrates misoriented 5° towards the ;In planes. Both n-and p-type InSb were grown using TBDMSb or TDMASb and TMIn with mobilities up to 68,990 and 7773 cm2/V · s, respectively, at 77 K. The mobility for InSb using either TDMASb or TBDMSb was improved by going to lower temperatures (400°C), pressures (215 Torr) and V/III ratios (2–4). The surface morphology improved with higher temperature (475°C), and lower pressure (215 Torr), with little or no correlation to the V/III ratio. The growth of high mobility InSb with smooth surfaces at temperatures ≤ 425°C was not achieved with TDMASb or TBDMSb and TMIn under the conditions investigated in this work.

The growth of InAsSb/InGaAs strained-layer superlattices by metal-organic chemical vapor deposition

We have grown InAs{sub l-x}Sb{sub x}/In{sub 1-y}Ga{sub y}As strained-layer superlattice (SLS) semiconductors lattice matched to InAs using a variety of conditions by metal-organic chemical vapor deposition. The V/III ratio was varied from 2.5 to 10 at 475 C, at pressures of 200 to 660 torr and growth rates of 3 {minus} 5 {angstrom}/s and layer thicknesses ranging from 55 to 152 {angstrom}. Composition of InAsSb ternary can be predicted from the input gas molar flow rates using a thermodynamic model. At lower temperatures, the thermodynamic model must be modified to take account of the incomplete decomposition of arsine and trimethylantimony. Diodes have been prepared using Zn as the p-type dopant and undoped SLS as the n-type material. The diode was found to emit at 3.56 {mu}m. These layers have been characterized by optical microscopy, SIMS, x-ray diffraction, and transmission electron diffraction. The optical properties of these SLS`s were determined by infrared photoluminescence and absorption measurements.

The optimization of interfaces in InAsSb/InGaAs strained-layer superlattices grown by metal-organic chemical vapor deposition

We have prepared InAsSb/InGaAs strained-layer superlattice (SLS) semiconductors by metal-organic chemical vapor deposition (MOCVD) under a variety of conditions. Presence of an InGaAsSb interface layer is indicated by x-ray diffraction patterns. Optimized growth conditions involved the use of low pressure, short purge times, and no reactant flow during the purges. MOCVD was used to prepare an optically pumped, single heterostructure InAsSb/InGaAs SLS/InPSb laser which emitted at 3.9 {mu}m with a maximum operating temperature of approximately 100 K.