Surface and interface of GaAs/Sl-GaAs structures investigated by photoreflectance spectroscopy

Epitaxial layers of GaAs were grown by MOCVD technique on SI-GaAs substrates. Photoreflectance (PR) spectra were measured at room temperature for energies in the vicinity of the E(0) critical point for p-type as well as n-type doped GaAs/SI-GaAs structures. Two experimental methods for the further investigation of the obtained PR spectra were proposed. The first method was based on the gradual chemical etching of the doped epilayer, the second on the PR measurements carried out for different wavelengths of the laser pump beam. Depending on the doping concentration, the existence of two PR subsignals was observed: the first arises from the surface space charge region, the second from the interface region. In the computational analysis of measured PR spectra Kramers-Kronig analysis of the complex photoreflectance function was applied. (C) 1997 Elsevier Science Ltd.