Effect of Carbon Doping and Crystalline Quality on the Vertical Breakdown Characteristics of GaN Layers Grown on 200-mm Silicon Substrates

Abstract

We have carried out a systematic study on the vertical breakdown behavior of GaN-based epitaxial layers on 200-mm-diameter Si(111) substrates with different carbon concentrations. The GaN layers were grown by metalorganic chemical vapor deposition by tuning growth parameters such as temperature and pressure. This study shows that, when the carbon concentration of the wafers is below 1 × 10¹⁸ cm⁻³, the vertical leakage currents are high with breakdown voltages below 260 V. The wafers that reveal lower vertical leakage currents are those with moderate carbon doping concentrations (between ∼1 × 10¹⁸ cm⁻³ and 2.5 × 10¹⁸ cm⁻³), whereas wafers with higher carbon concentrations (≥4 × 10¹⁸ cm⁻³) give rise to poor breakdown behavior caused by lower crystal quality and rougher surface morphology. The uniformity of vertical breakdown behavior across a 200-mm wafer shows that wafers with low crystal quality also exhibit poor uniformity. Moreover, when the carbon doping level is relatively high (between ∼2 × 10¹⁸ cm⁻³ and 2.5 × 10¹⁸ cm⁻³), good uniformity with variation of ∼5% can be achieved.