Properties of narrow-bandgap (0.3–0.48 eV) A3B5 solid solution epilayers grown by metal-organic chemical vapor deposition

Abstract

Active regions of mid infrared range (1.7-5 μm) semiconductor devices can be fabricated using anti mony containing A 3 B 5 solid solutions lattice matched to InAs and GaSb substrates. At present, double heterostructures for the 3.4-5 μm spectral range devices are usually manufactured on InAs sub strates, and bulk materials InAs and InAsSb [1] as well as superlattices formed by layers of strained ternary solid solutions InAsSb, InAsP and InGaAs [2] are usu ally used as active regions of light emitting sources.InAsPSb solid solutions are mostly used for clad ding layers. The InAsSb ternary solid solutions do not have lattice matching to InAs, and, therefore, for defectless coupling of such active regions with InAsPSb claddings, the cladding layers must be lat tice matched to InAsSb. To allow such lattice match ing, a gradient layer with varying lattice constant has been grown on the substrate [3].Attractive materials for fabrication of the active regions of the device structures for the 3.4-5 μm spec tral range are narrow bandgap quaternary solid solu tions, as they allow layers lattice matched to the sub strate to be obtained. The InAsPSb solid solutions lat tice matched to InAs at room temperature cover the bandgap range 0.35-0.6 eV, which corresponds to the 2.1-3.6 μm spectral range. The GaInAsSb solid solu tions lattice matched to InAs at room temperature cover the bandgap range 0.25-0.68 eV, which corre sponds to the 1.8-5 μm spectral range. In [4], the GaInAsSb solid solutions were used for growth of active regions of light emitting diodes working at wavelength 3.7 μm.At present, developing A 3 B 5 metal organic chemi cal vapor deposition (MOCVD) technology is press ing, because this method is the most commonly used industrial manufacturing of device structures. One of the parameters characterizing the MOCVD process is the ratio of the sum of partial pressures of the V group components precursors to that of the III group com ponents precursors-V/III. MOCVD setups allowing growth only at atmo spheric pressure are widespread. On such setups, a wide composition range of InAsPSb solid solutions on InAs substrates at V/III = 100 [5] and GaInAsSb on GaSb substrates at V/III = 0.8-5 [6] were obtained. Other values of V/III for InAsPSb solid solutions grown at atmospheric pressure were also reported: V/III = 10.3 for InAs 0.65 P 0.24 Sb 0.11 [7] and V/III = 40 for InAs 0.27 P 0.5 Sb 0.23 [8,9].Low pressure MOCVD allows improving the qual ity of obtained epilayers due to increasing the unifor mity of distribution of components on the area, as well as decreasing the probability of parasitic reactions with adduct formation, as reported in [10], where perfect epilayers of GaInAsP solid solutions on InP substrates in the complete range lattice matched to InP compo sitions have been grown. Moreover, at low pressure MOCVD, the consumption of hydrides and metal organic compounds forming the epilayers decreases. An important advantage of low pressure MOCVD is a high speed of gas mixture replacement, which allows sharper heter...