High mobility GaN drift layer on Si substrates: The role of surface N vacancy on carbon incorporation

Abstract

The control of carbon (C) impurity plays a crucial role in achieving high mobility GaN drift layers for GaN vertical power devices. We investigate the effects of NH3 partial pressure on the C incorporation in GaN and find out that the NH3 partial pressure is the key parameter controlling the C concentration. It is found that the C concentration is inversely proportional to the square of NH3 partial pressure under a fixed growth rate. Further physical analysis indicates that higher NH3 partial pressure results in a lower surface N vacancy (VN) concentration and, thus, the lower C incorporation efficiency. Under such a guidance, the C concentration in GaN can be reduced to as low as ∼1.7 × 1015/cm3 at a growth rate of 1 μm/h. As a consequence, a record high electron mobility of 1227 cm2/V·s at the room temperature is achieved for a GaN drift layer grown on Si substrates. Our strategy is effective in C control and paves the way for realizing high performance kV-class GaN vertical power devices on Si substrates.