Influence of indium segregation on the light emission of piezoelectric InGaAs/GaAs quantum wells grown by molecular beam epitaxy

Abstract

Pseudomorphic $In_{0.2}Ga_{0.8}As/GaAs$ quantum wells (QWs) were grown by molecular beam epitaxy (MBE) on GaAs substrates oriented along the (11n) direction, with n=1,2,3,4. The optical and structural properties of the heterostructures were studied by photoluminescence spectroscopy (PL) at 14, 77 and 300 K, and atomic force microscopy (AFM) measurements. The emission wavelength from the QWs has two contributions, a blue shift due to the compressive strain, and a red shift due to the quantum confined Stark effect produced by the piezoelectric field present in these materials. A traditional theoretical interpretation of the QWs emission employing a simple well model shows discrepancies with the experimental results. In order to satisfactorily explain the emission wavelength we proposed to include segregation effects of In at the wells interfaces. The matrix transfer method was implemented to solve numerically the Schrödinger equation taking into account In segregation effects by including an asymmetric potential well with a profile depending on the details of the In incorporation. With segregation effects included in the emission calculations, the theoretical predictions reproduce very well the experimental values of PL emission. Our results demostrate that in order to have efficient InGaAs QWs-based optoelectronic devices is very important to take into account interfacial segregation effects.