GaN lattice damage and GaN-HEMT metrology by cameraless T-ray imaging

Abstract

Gallium nitride (GaN) film grown on a silicon substrate has been investigated for high electric field induced lattice damage via cameraless terahertz (T-ray) imaging technique. In addition, T-ray time-domain spectroscopy (TGS) has been conducted on the same GaN film as a function of depth via nondestructive and noncontact pump-probe technique. This is termed as the deep-level TDS. Further, a pair of GaN high electron mobility transistor (HEMT) dies have been imaged at the channel area where the deep-level TDS has also been conducted. A pristine die has been compared with a similar die that was irradiated with mild nuclear radiation. The channel width measured via T-ray metrology of both dies matches those determined from the optical microscope images. However, T-ray deep-level spectral analysis of both dies reveal that the pristine die’s channel structure remains unaffected up to 5.5 THz up to a depth of 3 µm while that of the irradiated die’s channel structure’s performance is shrunk to 4.2 THz to the same depth of 3 µm. details of data and analysis have been discussed. The technique may be deployed to other similar systems and devises.