Growth, microstructure, and luminescent properties of direct-bandgap InAlP on relaxed InGaAs on GaAs substrates

Abstract

Articles you may be interested inEffects of doping and grading slope on surface and structure of metamorphic InGaAs buffers on GaAs substrates Direct-bandgap InAlP alloy has the potential to be an active material in nitride-free yellow-green and amber optoelectronics with applications in solid-state lighting, display devices, and multi-junction solar cells. We report on the growth of high-quality direct-bandgap InAlP on relaxed InGaAs graded buffers with low threading dislocation densities. Structural characterization reveals phase-separated microstructures in these films which have an impact on the luminescence spectrum. While similar to InGaP in many ways, the greater tendency for phase separation in InAlP leads to the simultaneous occurrence of compositional inhomogeneity and CuPt-B ordering. Mechanisms connecting these two structural parameters are presented as well as results on the effect of silicon and zinc dopants on homogenizing the microstructure. Spontaneous formation of tilted planes of phase-separated material, with alternating degrees of ordering, is observed when InAlP is grown on vicinal substrates. The photoluminescence peak-widths of these films are actually narrower than those grown on exact (001) substrates. We find that, despite phase-separation, ordered direct-bandgap InAlP is a suitable material for optoelectronics. V C 2013 AIP Publishing LLC.

Amber-green light-emitting diodes using order-disorder AlxIn1−xP heterostructures

“…Color contrast stripes weakly visible within the active layer are attributed to composition modulation of the Al x In 1-x P film. 26 Figure 1(c) shows representative transmission electron diffraction (TED) images from each cladding layer and from the active region of the device. The superspots visible in the active region TED image indicate the presence of both variants of CuPt-B ordering.…”

Determination of the direct to indirect bandgap transition composition in AlxIn1−xP

“…12,13 The lack of atomic ordering was verified using transmission electron diffraction measurements in a transmission electron microscope (TEM). A more complete discussion of the growth of Al x In 1Àx P using the above described method, along with TEM images of the graded buffer layers and disordered Al x In 1Àx P material, can be found in Mukherjee et al 11 All Al x In 1Àx P epi-layers are nominally 700 nm thick and are observed to be pseudomorphically strained to the In y Ga 1Ày As buffer layer based on XRD reciprocal space mapping. Samples discussed in this article are all compressively strained to the In y Ga 1Ày As, where the strain in all cases is less than 0.37%.…”

“…A set of bulk Al x In 1Àx P samples closely lattice matched to InGaAs graded buffer layers were grown on GaAs substrates using MOCVD. 11 Simultaneous observation of direct and indirect transitions by photoluminescence (PL) yields a precise value of x c ¼ 40.5% at low temperatures in completely disordered alloys at low temperature. Implications for the use of direct bandgap Al x In 1Àx P alloys in solid-state lighting applications are also discussed.…”

Recombination activity of threading dislocations in GaInP influenced by growth temperature

“…Prior work on direct band gap AlInP in the same growth chamber showed no increase in oxygen incorporation as the growth temperature was lowered from 725 °C to 620 °C. 28 However, if continues to rise from a further increase in electron-hole separation due to the formation of larger ordered domains at 625 °C, it could become comparable to and result in a lowering of the emission intensity. In previous work on ordered AlGaInP quantum wells, which are known to have a higher order parameter than GaInP, was seen to increase by nearly an order of magnitude at room temperature compared to the disordered case.…”