The Effect Of Pretreatment On Gan Hemt Performance Before Sin Passıvatıon

Thesis Type: Postgraduate

Institution Of The Thesis: Gazi Üniversitesi, Fen Bilimleri Enstitüsü, Turkey

Approval Date: 2018




AlGaN/GaN heterostructures are promising semiconductors for next-generation high-frequency and high-power devices, particularly at high temperature and high voltage operation. Their wideband gap allows high breakdown voltage and high saturation current capabilities in an AlGaN/GaN high-electron mobility transistor (HEMT), which make them potential candidates for many different applications, such as wireless communications, satellite and radar applications. However, in this technology, there are some performance limits due to current leaks and current collapse. These effects are caused by surface defects, surface traps and surface damage. In this study, it is aimed to improve the performance by decreasing the current leakage by pretreatments made before the passivation layer deposition of the HEMTs. The AlGaN/GaN epitaxial HEMT structure is grown by metal organic chemical vapor deposition (MOCVD) system. In the fabrication step, photomask and maskless patterning process, physical and chemical etching, metal coating, passivation layer deposition were done. Dry plasma pretreatments including SF6 and O2, CF4 and O2, NH3, N2 gases and wet chemical pretreatment of buffer oxide etchant (BOE) were applied to reduce surface defects, traps and damage. Characterization was carried out both before pre-treatment and after pre-treatment. As a result of DC measurements and gate lag measurements, it has been shown that the reduction of gate and drain current leaks are provided by nitrogen containing plasma pretreatments.