V.A. Solov’ev

Room-temperature 3.9–4.3 μm photoluminescence from InSb submonolayers grown by molecular beam epitaxy in an InAs matrix

We report on molecular beam epitaxial growth of InSb submonolayer insertions in an InAs matrix, exhibiting intense mid-IR photoluminescence (PL) up to room temperature (RT). The InSb insertions are fabricated by an exposure of InAs surface to an antimony Sb4 flux. The nominal thickness of insertions grown at different temperatures (TS=400–485°C) ranges from 0.6 to 1.4 monolayer, as estimated from x-ray diffraction measurements of InSb∕InAs multiple submonolayer structures. This gives rise to the variation of the emission wavelength within the 3.9–4.3 μm range at RT. An integral PL intensity drop from 77 K to RT does not exceed 20 times.

Electrical characteristics of p-3C-SiC/n-6H-SiC heterojunctions grown by sublimation epitaxy on 6H-SiC substrates

Abstract Sublimation epitaxy in a vacuum (SEV) has been used to obtain p-3C–SiC/n-6H–SiC heteroepitaxial structures. Results of a study of epilayers (X-ray diffraction analysis, scanning electron microscopy involving secondary electrons and electron beam induced current modes) and diode structures on their base ( I – V and C – V characteristics, electroluminescence spectra, DLTS) are presented. Band discontinuities are determined and a band diagram of the p-3C–SiC/n-6H–SiC heterostructure is constructed.

High-dose Al-implanted 4H-SiC p+-n-n+ junctions

p+-n-n+ junctions were fabricated by ion implantation with Al of low-doped epitaxial n layers of 4H-SiC grown by chemical vapor deposition on commercial 4H-SiC wafers both with and without reduction of micropipe densities. It was shown that, using high levels of Al ion doping (5×1016 cm−2) in combination with rapid thermal anneal, single-crystal p+-4H-SiC layers can be obtained. These layers do not form barriers at the contact metal–semiconductor interface and do not introduce additional resistance into structures with p+-n junctions. This significantly reduces the forward voltage drop across the structure in a wide range of current densities up to 104 A cm−2.

A 2.78-μm laser diode based on hybrid AlGaAsSb/InAs/CdMgSe double heterostructure grown by molecular-beam epitaxy

A mid-IR laser based on a hybrid pseudomorphic AlGaAsSb/InAs/CdMgSe heterostructure with a III–V/II–VI heterovalent interface at the 0.6-μm-InAs active region has been fabricated by molecular-beam epitaxy on p+-InAs substrate. It provides ∼1.5-eV asymmetric barriers for both electrons and holes in InAs, inhibiting carrier leakage from the active region. Despite a nonoptimal defect density at the CdMgSe/InAs interface (106–107 cm−2), the structure demonstrates lasing at ∼2.78 μm (up to 100 K) under pulse injection pumping with the threshold current density of 3–4 kA/cm2. The proposed design is promising for high-power mid-IR lasers operating at room temperature.

Temperature-dependent photoluminescence from type-II InSb∕InAs quantum dots

We report on the photoluminescence (PL) studies of InSb-enriched quantum dots (QDs) which are grown by molecular beam epitaxy in an InAs matrix. InSb∕InAs heterostructures have a nominal thickness of InSb insertions in the range of 0.6–2 monolayers and exhibit bright PL up to room temperature in the mid-infrared spectral range. The PL temperature dependence gives evidence that each InSb insertion can be regarded as an ensemble of QDs subject to carrier transfer even at low temperatures. Both QD PL energy and line-shape variations with temperature can be described employing Fermi-Dirac carrier statistics.

Asymmetric AlAsSb/InAs/CdMgSe quantum wells grown by molecular-beam epitaxy

Asymmetric (6.7–300)-nm-thick InAs quantum wells (QWs) confined between AlAsSb and CdMgSe barriers have been fabricated by molecular-beam epitaxy. A special procedure of the CdMgSe-on-InAs growth initiation, exploiting an ex situ S passivation of InAs and in situ deposition of an ultrathin ZnTe buffer layer, results in the fabrication of high quality structures with a density of extended defects below 106 cm2. QW photoluminescence studies demonstrate a confinement effect and confirm the type I band alignment at the heterovalent InAs/CdMgSe interface mediated by the ZnTe interlayer. Observation of Shubnikov de Haas oscillations of magnetoresistance for an asymmetric 19-nm-thick InAs QW indicates an existence of the two-dimensional electron gas with the low-temperature sheet electron density of 1.3×1012 cm−2 and the mobility as high as ∼10 000 cm2/V s.

Structural, electrical, and optical properties of low-doped 4H–SiC chemical vapor deposited epitaxial layers

Results of complex studies of structural, optical, and electrical characteristics of 4H–SiC n-type low-doped epitaxial layers grown by the chemical vapor deposition (CVD) method are presented. Characteristics of CVD layers grown on commercial wafers with and without a thin (<0.1 μm) buffer layer grown by liquid phase epitaxy (LPE) between the commercial wafer and CVD epitaxial layer were compared. It has been shown that the LPE filling process caused a significant improvement in the structural quality of CVD layers. Cathodoluminescence (CL) data and electrical characteristics of Schottky barriers (SB) revealed that the LPE layer also made the concentration profiles of the uncompensated donors and recombination centers for holes as well as the hole diffusion lengths more uniform over the CVD layer. According to CL and secondary ion mass-spectroscopy measurements the presence of aluminum as an impurity was detected in initial commercial wafers, as well as having LPE and CVD epitaxial layers. Forward current...

Defect-induced island formation in CdSe/ZnSe structures

Island formation in CdSe/ZnSe superlattice (SL) structures with a moderate defect density is investigated in a sub-monolayer range of CdSe nominal thicknesses. Besides the spontaneous formation of CdSe-enriched islands in defect-free regions, presence of dislocations crossing the SL causes an emergence of the defect-attached islands. The island location near interceptions of CdSe sheets with the dislocations produces a staircase ordering of the islands in neighboring SL layers. Such a mutual alignment of the CdSe-enriched islands results in modified optical properties of the defect-containing structures. Density and type of the defects promoting the laterally inhomogeneous incorporation of Cd are controlled, in general, by the initial stage of MBE growth and a lattice mismatch between ZnS(Be)Se cladding layers and a GaAs substrate.

Exchange interaction of electrons with Mn in hybrid AlSb/InAs/ZnMnTe structures

Diluted magnetic semiconductor heterovalent AlSb/InAs/ZnMnTe quantum well (QW) structures with an electron channel have been designed and grown applying molecular-beam epitaxy. The enhanced magnetic properties of QWs as a result of the exchange interaction with Mn2+ ions, are proved by measuring the microwave radiation induced spin polarized electric currents.

MBE growth and photoluminescence properties of strained InAsSb/AlSbAs quantum wells

Summary form only given. The InAsSb/AlSbAs heterojunction system is promising for mid-infrared (2-5 /spl mu/m) lasers, since it combines the narrow band gap of an InAsSb alloy (< 0.4 eV at 77K) with a large conduction band offset at the hetero-boundary. The use of a strained quantum well (QW) active layer instead of thick InAsSb one is believed to increase the differential gain and reduce considerably the Auger recombination which limits the maximum operating temperature of such lasers. We report on MBE growth and photoluminescence (PL) properties of compressively strained InAsSb/AlSbAs single QW heterostructures. A set of norminally-undoped structures with well widths varying from 4 to 20 nm was grown pseudomorphically on GaSb [001] substrates using a two-stage growth regime. PL measurements of the structures were performed at 80K. Temperature and pump-power dependences of the PL intensities versus various structure parameters will be discussed.