Investigation of buried homojunctions in p-InP formed during sputter deposition of both indium tin oxide and indium oxide

Abstract

Although it is apparent that direct current (dc) magnetron sputter deposition of indium tin oxide (ITO) leads to the formation of a buried homojunction in single crystal p-type InP, the actual mechanism of type conversion of the InP surface is not clear, nor is it immediately obvious how further improvements may be achieved. Previously, we have suggested that type conversion is caused by indiffusion of Sn during the ITO deposition process and additionally demonstrated that this effect is strengthened by the presence of hydrogen in the sputtering gas. Recently, however, efficiencies of almost 17% (Global) have been achieved for cells fabricated by sputter depositing In2O3(IO) alone, strongly suggesting that the Sn may not be an essential part of type conversion. In this work, a variety of electrical and optical techniques has been used to assess the changes at the ITO/InP and IO/InP interfaces. From these, it is concluded that several mechanisms, including passivation of acceptors by hydrogen and ‘‘sputter damage,’’ occur simultaneously. This analysis suggests several directions for further improvement of these devices.