Performance Analysis Of ALGaN/GaN Field Effect Schottky Diode

GaN-based semiconductor material processes the advantages of wide band gap，high electron drift velocity，high heat conductivity, high resistance of corrosion andradiation, etc.. It’s well suited to fabricate electronic devices used in high temperature，high frequency，high power applications. Conventional GaN schottky barrier diode(SBD) can deliver high breakdown voltage, while AlGaN/GaN hetero junctionfield-effect schottky barrier diode (FESBD) with a schottky contact formed by metalswith different barrier heights (SBH) shows both high reverse breakdown voltage andlow positive turn-on voltage and is very suitable to use as a flyback diode in thecircuits with inductive load. This thesis focuses on the device performance simulationof AlGaN/GaN FESBD and the device optimization.The reverse breakdown characteristic simulation is successfully accomplished bycalculate the conventional SBD I-V characteristics based on pure GaN，pure AlGaNand the AlGaN/GaN hetero junction. It is obtained the dependence of devicebreakdown voltage on the material parameters such as background dopingconcentration and etc. the reasonable model and parameter value range are ascertained.With analysis of how the schottky barrier height of AlGaN/GaN SBD influencethe device performance, it is investigated how the ways to form a composite schottkycontact with different metals for a SBD, i.e. high SBH surrounded by low SBH or theopposite, work on the device characteristics. It’s found that since the peak electric fieldin the device appears at the edge of the anode closer to the cathode, the two kinds ofcomposite schottky contacts lead to totally different device performance. The formershows performance similar to SBD with low SBH, the latter shows the performance ofhigh reverse breakdown voltage and low positive turn-on voltage, desirable for theFESBD. It is found the high barrier at the edge of the anode ensures the highbreakdown voltage, which equal to that of the high barrier AlGaN/GaN SBD, the lowbarrier at the centre of the anode leads to large forward current and low turn-onvoltage.It is found when changing the area ratio of high SBH metal to low SBH metal inthe anode of FESBD that increasing the area of low SBH metal results in largerforward and reverse current, but the reverse breakdown voltage remains unchanged inconsiderable large range of the area ratio from5:1to1:9. This is useful in optimizing the device structure and reducing the device processing cost on the noble metal usingas high SBH metal.