Effect of GaN cap layer towards ohmic contact of open-gate Cr AlGaN/GaN high electron mobility transistor

Metal-organic chemical vapour deposition (MOCVD) was used to grow AlGaN/GaN high electron mobility transistor (HEMT) on a sapphire substrate with different thicknesses of the GaN cap layer from 1.5 nm to 2.5 nm for open-gate chromium (Cr) AlGaN/GaN HEMT structures. High-resolution X-ray diffraction (HRXRD) was utilised to investigate the structural characteristics of the materials. A non-annealing technique was used to reduce the negatively impacted on the electrical properties is bad for the function of the device. The use of the GaN cap layer improved the performance of the devices as the resistance decreased with increasing the thickness of the GaN cap layer. Here we demonstrate the comparison between different thicknesses of GaN cap layers to improve the resistivity of the device.