Low-Dispersion, High-Voltage, Low-Leakage GaN HEMTs on Native GaN Substrates

Abstract

Abstract-In this work the advantages of GaN HEMTs grown on native GaN substrates over GaN/Si or GaN/Sapphire substrates are investigated, and correlated with epitaxial quality. TEM plane view and cross section analysis of GaN/GaN revealed dislocation density lower than 1 × 10 6 cm −2 , which is at least 3 orders of magnitude lower than the case of GaN/Si or GaN/Sapphire. In the case of GaN/Si, the dislocations did not necessarily originate from the substrate/nucleation layer interface, but the strain relief and isolation buffer stacks were main contributors to the dislocation density. GaN/GaN HEMTs demonstrated superior electrical and thermal performance. GaN/GaN demonstrated 3 orders of magnitude lower off-state leakage, current collapse (Ron increase) after stress bias less than 15% compared to 50% in the case of GaN/Si, and 2% drop of the onstate current due to self-heating in DC operation as compared to 13% and 16% for GaN/Si and GaN/Sapphire respectively. The GaN/Si thermal performance approached GaN/GaN only by substrate removal. Therefore GaN/GaN can allow high on-state current, low off-state leakage current, minimal current collapse, and enhanced thermal dissipation capability at the same time, which can be directly correlated to the absence of high dislocation densities.

AlGaN/GaN on SiC Devices without a GaN Buffer Layer: Electrical and Noise Characteristics

“…Aluminium gallium nitride/gallium nitride (AlGaN/GaN) high electron mobility transistors (HEMTs) are widely used in high-power and high-frequency applications due to their superior characteristics based on the unique physical properties of III-nitride materials. The AlGaN/GaN heterostructures can be grown on sapphire, silicon, silicon carbide, and native GaN substrates [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ]. While sapphire and silicon substrates are the most cost-effective, the best characteristics are achieved on transistors fabricated on silicon carbide (SiC) and GaN substrates.…”

Room Temperature 2DEG Mobility Above 2350 cm2/V·s in AlGaN/GaN HEMT Grown on GaN Substrate

“…At this time, dislocations formed a clear boundary between the substrate and the epitaxial layer, which can be observed in the TEM images. 29,34 Figure 4a covers the entire thickness of the HEMT structure, the interface region between epilayer and substrate and a part of the GaN substrate. The boundary is not visible in the TEM image, and the interface between the substrate and the epitaxial layer can only be inferred from the thickness.…”

“…Using the native GaN substrate is a promising approach to address these problems. By reducing the dislocation density by several orders of magnitude, 8,9 device performance and reliability can be efficiently improved.…”

Temperature Dependent Vertical Conduction of GaN HEMT Structures on Silicon and Bulk GaN Substrates

“…This direct lattice‐matched epitaxy leads to a significant reduction in defect density and threading dislocations density. GaN on GaN HEMTs showing superior electrical performance have been reported recently . This is pronounced in three orders lower off‐state leakage and reduced current collapse when being compared to HEMT on Si and sapphire substrates which is correlated to a reduced dislocation density due to homoepitaxy.…”