Abstract
We report on the influence of deep pits on three terminal-off breakdown of AlGaN/GaN high electron mobility transistors (HEMTs) grown on 4-in. silicon by metalorganic chemical vapor deposition (MOCVD). For devices with deep pits, the breakdown was greatly affected by excess leakage through buffer and substrate. The reason for excess leakage was established using transmission electron microscope (TEM) image. The TEM image reveals that deep pits originate from silicon substrate because of Ga etching Si substrate at high growth temperatures. These etch pits and their surface termination in the form of hexagonal pyramid pits act like micro-pipes causing high leakage through the substrate and buffer. The three terminal-off breakdown of the HEMTs decreased rapidly as the density of deep pits increase.
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