Electrical and optical properties of p-type ZnO

ZnO has ideal qualities for bright, efficient UV light emitting diodes and laser diodes, based on p–n junctions. However, while high quality n-type ZnO has been available for many years, the development of good p-type material is a much more recent phenomenon. The most successful acceptor dopants have been the group V elements, N, P and As; N substitutes on the O site, but the exact structures of the P and As acceptors have not yet been established. Resistivities as low as 0.4 Ω cm have been measured, and some UV heterojunction and homojunction LEDs have been fabricated. Optical fingerprints of p-type ZnO often include a photoluminescence line at 3.31 eV, and strong donor-bound exciton lines at 3.357 and 3.367 eV, both of which are well known from previous studies of n-type ZnO.