Investigation of Low Frequency Noise Properties of Wide Gap Semiconductors, SiC and GaN, and the Main Properties of the SiC Based Power Devices, Diodes and Thyristors

摘要

Low frequency noise properties of SiC, GaN, and SiC and GaN-based structures have been investigated. At elevated temperatures, the main contribution to low frequency noise in SiC structures comes from a surface local level. A method is proposed for extracting parameters of local surface levels in semiconductors from noise spectroscopic data. It has been shown that the level of flicker noise in GaN strongly depends on the structural perfection of the material. The nature of the 1/f noise in GaN can be similar to that in GaAs and Si. The 1/f noise is caused by the fluctuations of the occupancy of the tail states near the band edges. The systematic comparative investigation of the low frequency noise in GaN/GaAlN HEMTs has been provided in the temperature range 300 < T < 550 K for the structures grown under identical conditions on sapphire and SiC substrates. The results obtained show that the level of 1/f noise is appreciably less for the samples on SiC substrates compared with those grown on sapphire. The Hooge parameter alpha for the wafers grown on SiC can be as small as alpha = 10(exp -4). The effect of gate leakage current, surface states, levels in GaAlN, and noise channel on the total noise of GaAlN HFETs and MOS- HFETs has been investigated.