Metastability of Band-Gap Energy in GaInNAs Compound Investigated by Photoreflectance

Abstract

The band-gap energy of GaInNAs layers lattice-matched to GaAs substrate and annealed under different temperatures is investigated by photoreflectance spectroscopy. Different nitrogen nearest-neighbor environments of N atom appear in GaInNAs layers due to the post-growth annealing. It leads to an energy-fine structure of the band gap, i.e. well separated photoreflectance resonances related to different nitrogen nearest-neighbor environments (N-Ga4−mInm (0 ≤ m ≤ 4) short-range-order clusters). The temperature dependence of the band gap E(T ) related to different N-Ga 4−m In m clusters is investigated in 10-280 K temperature range, and Varshni and Bose-Einstein parameters for E(T ) are determined.

Studying the microscopic clusters involving N in dilute GaIn(Al)NAs alloys via local mode spectroscopy and computer simulation

“…Although the two experimental results (see Table 2) provided different values of LVMs, both have confirmed the preferential bonding with a significant fraction of substitutional nitrogen attached at least to one Ga-neighbour. In the MBE grown low-In content layers of Ga 1-x In x N y As 1-y with x = 0.058 and y = 0.028, the annealing induced blue-shift of the band gap has recently been suggested to the changes in the photo-reflectance resonances [24] associated with three different N-centred shortrange clusters (N-Ga 4 , N-Ga 3 In 1 , and N-Ga 2 In 2 ). Although the mechanism for the redistribution of N environment from Ga-(In-) ligand rich sites to In-(Ga-) ligand rich sites is not well understood, the hopping of N or vacancy assisted migration of In and Ga atoms at elevated temperatures is speculated for the rearrangement of group III-N-As bonding.…”