Mechanistic influence on uniformity of sheet resistance of AlGaN/GaN HEMT grown on Si substrate with the graded AlGaN buffer layers

In this study, the relationship among the wafer bow, dislocations, and transport characteristics of aluminum gallium nitride/gallium nitride (AlGaN/GaN) high electron mobility transistor (HEMT) grown on the silicon substrate using conventional AlGaN buffer layers was comprehensively investigated. It is speculated herein that the mechanism that affects the uniformity of sheet resistance is the uneven distribution of stress in GaN-based HEMT and the wafer bow it generates. The bow can lead to the difference in mobility through affecting the threading dislocations, resulting in poor uniformity of resistance. This conjecture was supported by the results of high-resolution X-ray diffraction, non-contact Hall measurement, Raman spectroscopy , and sheet resistance measurements. To further investigate this problem, a model was proposed to explain it from the perspective of formation mechanism. • Mechanism affecting the uniformity of sheet resistance of HEMT is investigated. • Models are proposed to explain the influence of the wafer bow on dislocations. • Relationship among the bow, dislocation, mobility and sheet resistance is clarified. • A AlGaN/GaN HEMT with improved uniformity of sheet resistance is obtained.