Deep‐level defects induced by Ar‐ion beam etching in n‐type Al_xGa_1‐xAs grown by MBE

Abstract

Results of the electrical study of the damage caused by Ar-ion beam etching in MBE grown Al x Ga 1-x As : Si laser diode material are reported. This study has involved measurements of capacitance as a function of voltage and temperature as well as deep level transient spectroscopy measurements on Schottky-barriers diodes. The Schottky contacts were fabricated conventionally by depositing Au in a vacuum onto the etched AlGaAs surface. For a reference the Schottky diodes of the best quality were produced in-situ by evaporation of Al on the top of the epi-layer at the end of the MBE growth run. On the basis of the results of a comparative study deep-level defects related to the subsurface damaged layer have been recognised. Emission signatures as well as depth profiles of the defect concentration have been studied and analysed. Moreover, DLTS spectra revealed the presence of a well-known DX(Si) centre and M-type defect related level attributed to a vacancy and impurity complex. The presence of an additional deep-level defect located in the lower half of the energy gap that was induced by dry etching is also suggested. An extra defect considered has the high enough concentration to disturb carrier spatial profiles and DX centre characteristics. It is suggested that it may be responsible for degradation effects in GaAs/AlGaAs heterostructure lasers, which fabricating involves dry etching.