Observation of ”negative” persistent photoconductivity effect at T > 200 oC in N-polar GaN/AlGaN/GaN heterostructures

It is rarely reported that semiconductor materials can exhibit the ”negative” persistent photoconductivity (PC) effect. In this work the ”negative” persistent PC effect was observed in the Nitrogen (N)-polar oriented GaN/AlGaN/GaN heterostructure under the sub-bandgap illumination (2.0-2.8 eV) in the temperatures range of 200-250 oC. This is the first observation of the negative persistent PC effect in semiconductor materials at such high temperatures. The phenomenon was explained based on the model, which assumes the interaction between the absorbed oxygen species on the N-polar GaN surface, the DX centers in the GaN channel layer and two-dimensional electron gas at GaN/AlGaN interface. The discovery of high temperature ”negative” persistent PC in N-polar III-nitrides heterostructures may lead to novel applications such as temperature stable optical memories.