Characteristics of ZnO/GaN heterostructure formed on GaN substrate by sputtering deposition of ZnO
The n-ZnO/p-GaN heterostructures were formed by the growth of n-type ZnO layer using a sputtering method onto p-type GaN substrate which had been grown by a metal organic chemical vapor deposition. The samples showed the mirror-like surface and ultraviolet emission properties. For measurements of high-resolution X-ray diffraction, the samples exhibited the (0 0 0 l) peaks corresponding to both ZnO and GaN single crystals. And also, the peaks from interfacial layer of metastable Ga2O3 appeared eventually. The heterojunction diode fabricated using these heterostructured layers clearly showed the rectifying behavior. However, no relevant but very weak electroluminescence signal was detected. This result is attributed to the existence of metastable Ga2O3 interfacial layer having lots of interface states acting as nonradiative recombination centers.
Fig. 1. Top-view SEM images of ZnO layers grown on GaN substrates at 600 °C under mixture gases of: (a) Ar:O2 = 50 sccm:0 sccm, (b) Ar:O2 = 50 sccm:25 sccm, (c) Ar:O2 = 50 sccm:50 sccm, and (d) Ar:O2 = 50 sccm:75 sccm.
Source:Journal of Crystal Growth