CdS induced homojunction formation in crystalline p-CuInSe₂

The deposition of CdS onto single-crystal p-CuInSe₂ (at a substrate temperature of 200°C) results in a CuInSe₂ homojunction rather than the expected heterojunction. Junction depths, varying from 1 to 9 μm, correlated well with the free-carrier concentration of the sample crystals. The junction depths were measured by electron-beam-induced current line scans of cleaved junctions and were corroborated by quantum efficiency measurements. All the materials deposited to date (CdS, Cd, Au, and Mo) have resulted in type conversion of the CuInSe₂. The experimental evidence for this type conversion is presented and possible defect chemical origins identified.