Deep donor-acceptor pair recombination in InGaAs-based heterostructures grown on InP substrates

• Published in: Journal of applied physics 2005-11, Vol.98 (9), p.093708-093708-6
• Main Authors: Gfroerer, T. H., Gillespie, C. E., Campbell, J. P., Wanlass, M. W.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.2126153

We are investigating a series of lattice-matched In x Ga 1 − x As ∕ In As y P 1 − y double heterostructures with indium concentrations ranging between x = 0.53 and x = 0.78 . The double heterostructures incorporating indium-rich alloys ( x > 0.53 ) experience lattice mismatch relative to the InP substrate. Previous work has produced convincing but indirect evidence that the distribution of defect levels in the In x Ga 1 − x As changes dramatically when the epistructure deviates from the lattice-matched condition. In particular, deep midgap states appear to give way to shallower near-band-edge states with increasing mismatch. Here, we report sub-band-gap photoluminescence measurements that explore these changes directly. We observe a broad low-energy peak in the spectra of the lattice-matched and nearly lattice-matched epistructures that is not present in the more mismatched case. The sub-band-gap emission blueshifts and grows superlinearly with photoexcitation up to and exceeding 1000 W ∕ cm 2 . This unusual behavior is attributed to transitions between ordinary acceptor levels and deep, defect-related donorlike states. We find no evidence for the shallower defect states that we expected to arise with increasing lattice mismatch.