High-performance, micromachined GaN-on-Si high-electron-mobility transistor with backside diamondlike carbon/titanium heat-dissipation layer

A micromachined AlGaN/GaN high-electron-mobility transistor (HEMT) on a Si substrate with diamondlike carbon/titanium (DLC/Ti) heatdissipation layers was investigated. Superior thermal conductivity and thermal expansion coefficient similar to that of GaN enabled DLC/Ti to efficiently dissipate the heat of the GaN power HEMT through the Si substrate via holes. This HEMT with DLC design also maintained a stable current density at bending conditions (strain: 0.01%). Infrared thermographic imaging showed that the thermal resistance of standard multi-finger power HEMT layer was 13.6 K/W and it improved to 5.3 K/W because of the micromachining process with a backside DLC/Ti composite layer. Thus, the proposed DLC/Ti heat-dissipation layer realized efficient thermal management in GaN power HEMTs.