Wide Band-Gap II-VI Compound Semiconductor Grown by MOCVD and its Application to Blue Laser Diodes

Abstract

We have spent a great deal of effect in GaN as well as in ZnSe due to the rapid and more prom1smg development of GaN recently. We have performed intenstive material study on GaN, such as DLTS, TSC, photocurrent spectroscopy, and x-ray, to understand its defect nature. The maJor __achievements of last year's work in our laboratory can be summarized as follows. (1)We are the first group to observe the transferred-electron effect in GaN. We observed a negative differential resistivity (NOR) in GaN under high electric field. The threshold electrical field was found to be around l.9lxl05 V/cm. The NDR of GaN can be used in the application of high-temperature Gunn diodes. (2)We have performed a systematic studies on GaN M-S-M ultraviolet detectors made from GaN grown by MOCVD under different NH3 flow rates. We have found that a 0.62 eV deep trap which was att􀀧buted to gallium antisites or nitrogen vacancy-related defects was responsible for the low respons1v1ty _and the slow response time in GaN UV detectors. In addition, this 0.62 eV level can be effectively reduced by increasing the NH3 flow rate during the MOCVD growth. As a result, a high-perform􀁉n􀁊e UV 􀁋etector was fabricated on GaN of the lowest 0.62 eV trap. This detector has a respons1v1ty as high as 3200 A/W under 5 V at a wavelength of 365 nm and improved response times in the sub-milliseconds range.