High-quality InAsyP1−y step-graded buffer by molecular-beam epitaxy

Abstract

Relaxed, high-quality, compositionally step-graded InAsyP1−y layers with an As composition of y=0.4, corresponding to a lattice mismatch of ∼1.3% were grown on InP substrates using solid-source molecular-beam epitaxy. Each layer was found to be nearly fully relaxed observed by triple axis x-ray diffraction, and plan-view transmission electron microscopy revealed an average threading dislocations of 4×106 cm−2 within the InAs0.4P0.6 cap layer. Extremely ordered crosshatch morphology was observed with very low surface roughness (3.16 nm) compared to cation-based In0.7Al0.3As/InxAl1−xAs/InP graded buffers (10.53 nm) with similar mismatch and span of lattice constants on InP. The results show that InAsyP1−y graded buffers on InP are promising candidates as virtual substrates for infrared and high-speed metamorphic III–V devices.

The development of (InGa)As thermophotovoltaic cells on InP using strain-relaxed In(PAs) buffers

“…Investigators have successfully implemented stepgraded mixed group-III alloy buffers composed of (InGa)As or (InAl)As, but both of these approaches suffer from very rough morphologies and large residual strains [5,7]. In(PAs) buffers possess both a lower roughness for a similar amount of latticemismatch strain relief and a lower residual strain for a similar buffer thickness [8]. These improved physical characteristics are believed to be related to the superior performance of (InGa)As TPV cells fabricated using In(PAs) buffers [6,9].…”

Triple-axis X-ray reciprocal space mapping of InyGa1−yAs thermophotovoltaic diodes grown on (100) InP substrates

“…High-resolution X-ray diffraction (HRXRD) reciprocal space mapping (RSM) directly measures the in-plane and out-of-plane lattice parameters, strain, and the diffuse X-ray scattering from multilayered semiconductor heterostructures [3,4]. The technique was recently used to characterize strainrelaxation in linear and step-graded InP 1Àx As x and In 1Àz Al z As buffers grown by molecular beam epitaxy (MBE) [5][6][7]. Diffusely scattered X-ray intensity around reciprocal lattice point (RELP) maxima results from structural imperfections [4] that can potentially degrade the diode's electronic material quality and photovoltaic response due to defect-assisted minority carrier recombination.…”

Effect of epilayer's growth temperature on crystalline quality of InAs0.6P0.4/InP grown by two-step growth method

“…The problem can be reduced by growth of buffer layers with or without graded lattice parameters. A step-graded buffer layers in composition is often used to inhibit the dislocations to propagate towards the active layer of InAs x P 1−x materials [6]. But a single approach can simplify the growth procedure, such as the two-step growth method.…”