Molecular-beam epitaxial growth of InAs/GaAs superlattices on GaAs substrates and its application to a superlattice channel modulation-doped field-effect transistor

Abstract

The molecular-beam epitaxial growth conditions for (InAs)m(GaAs)n short period superlattices (SPSs) on GaAs substrates have been optimized by monitoring reflection high-energy electron diffraction (RHEED) intensity oscillations. The RHEED oscillation measurements enable understanding InAs growth behavior on a 7% lattice-mismatch GaAs substrate. Within one monolayer InAs deposition with lower than 560 °C growth temperature can give high SPS crystalline quality. The SPS periodic structure and the monolayer InAs formation, embedded in GaAs layers, have been confirmed by x-ray diffraction and transmission electron microscopy measurements. The obtained thickness controllability for the SPSs is less than±6% for InAs and ±3% for GaAs. The electron Hall mobilities for modulation-doped structures having an (InAs)1(GaAs)n SPS as an electron channel, whose layer index of n varied from 3 to 6, have been compared with those with a pseudomorphic InGaAs random alloy channel which has the equivalent In composition. The SPS channel samples have shown up to 15% higher electron Hall mobilities than the InGaAs alloy channel samples at 77 K. A 0.2-μm-gate (InAs)1(GaAs)6 superlattice channel modulation-doped field-effect transistor (FET) has exhibited a maximum extrinsic transconductance of as high as 450 mS/mm with a 70-GHz cut-off frequency at room temperature. The best noise figure of 0.58 dB with an associated gain of 11.15 dB has been attained. The obtained device characteristics are comparable or superior to those for the corresponding InGaAs alloy channel FETs. These results demonstrate, for the first time, the (InAs)m(GaAs)n SPS potentialities as an ordered counterpart for InGaAs random alloy for high-speed device applications.

InAs/GaAs short-period strained-layer superlattices grown on GaAs as spatial light modulators: uniformity measurements

“…The low temperature electron mobility of the field-effect transistor (FET) using InAs/GaAs monolayer superlattices was found to be one order of magnitude higher than that of InGaAs with the same impurity concentration, due to the suppression of alloy scattering [4]. A 15% improvement in electron Hall mobility for a modulation-doped FET (MODFET) using InAs/GaAs superlattices in place of an InGaAs alloy with equivalent In concentration was also observed [5]. Recently, a six-period (InAs) /(GaAs) SPSLS laser showed 29% lower threshold for a comparable laser with ternary active layers [6].…”

“…The fabrication of devices containing short-period strained-layer superlattices (SPSLSs) of all-binary (InAs) K /(GaAs) L composition has received much attention recently [1][2][3][4][5]. The low temperature electron mobility of the field-effect transistor (FET) using InAs/GaAs monolayer superlattices was found to be one order of magnitude higher than that of InGaAs with the same impurity concentration, due to the suppression of alloy scattering [4].…”

Higher mobility of charge carriers in InAs/GaAs superlattices through the elimination of InGaAs alloy disorders on GaAs

“…It results in a greater confinement and a higher concentration of carriers in InGaAs than in GaAs. The Toyoshima et al 10 measurements in a sample having a SPS channel, carried out at 77 K in darkness, show an increase up to 15% for the Hall mobility when compared with the InGaAs alloy channel samples. The scattering due to alloy disorder results from a random distribution of the atoms of the indium and gallium in the site of the group III element.…”

Photo-Hall studies of modulation-doped field-effect transistors with short-period superlattice channels rather than alloy channels

“…Despite the large lattice mismatch ͑7%͒ between InAs and GaAs, which produces a strained structure, the lattice mismatch can be accommodated by designing the layer thicknesses accordingly. [9][10][11][12][13][14] The conventional way 10,12,14 to characterize the SPS is by defining the number M of interfaces of InAs grown upon GaAs, the number N of interfaces of GaAs grown upon InAs, and the numbers m and n, measured in monolayers ͑ML͒, which define the InAs and GaAs layer thicknesses, respectively. The short form of the expression is M ͑InAs͒ m N͑GaAs͒ n .…”