Electron beam induced current profiling of the p-ZnO:N/n-GaN heterojunction

The high quality p-n structures studied consist of nitrogen doped ZnO:N films grown by plasma assisted molecular beam epitaxy on n-type GaN templates. The nitrogen concentration, determined by secondary ion mass spectroscopy, is about 1 × 10²⁰ cm⁻³. Temperature dependent photoluminescence studies confirm the presence of acceptor centers with an energy level lying approximately 130 meV above the valence band. The maximum forward-to-reverse current ratio I_F/I_R in the obtained p-n diodes is about 10⁷ at ±5 V, which is 2–5 orders of magnitude higher than previously reported for this type of heterojunctions. Electron-beam-induced current measurements confirm the presence of a p–n junction, located at the p-ZnO/n-GaN interface. The calculated diffusion length and activation energy of minority carriers are presented. The heterostructures exhibit strong absorption in the UV range with a four orders of magnitude high bright-to-dark current ratio.