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

Abstract

Abstract : We have spent a great deal of effect in GaN as well as in ZnSe due to the rapid and more promising development of GaN recently. We have performed intensive 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 (NDR) in GaN under high electric field. The threshold electrical field was found to be around l.91x10(exp 5) 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 attributed to gallium antisites or nitrogen vacancy-related defects was responsible for the low responsivity 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-performance UV detector was fabricated on GaN of the lowest 0.62 eV trap. This detector has a responsivity as high as 3200 A/W under 5 V at a wavelength of 365 nm and improved response times in the sub-milliseconds range.