Wafer-scale crack-free 10 µm-thick GaN with a dislocation density of 5.8 × 107 cm−2 grown on Si

Abstract

The increasing demand for complementary metal-oxide-semiconductor integrated GaN-based optoelectronics and power electronics calls for wafer-scale crack-free and high quality GaN thick film grown on Si. However, the huge mismatch in both lattice constant and coefficient of thermal expansion between GaN and Si often causes a high density of threading dislocations (TDD, typically 109–1010 cm−2) and the formation of micro-crack networks, producing a poor-quality GaN film with a limited thickness (<6 µm). By virtue of a well-designed Al-composition step-graded AlN/AlGaN buffer, a wafer-scale crack-free 10 µm-thick successive GaN with a low TDD of 5.8 × 107 cm−2 grown on Si was achieved for the first time. Detailed study on the depth-dependent strain and dislocation evolution shed light on the complex interplay between strain relaxation and defect reduction, as well as their influences on the GaN optical properties along the growth direction. This work paves the way for building high-performance GaN-based optoelectronics and power electronics on the Si platform.