Study On Structure Of High Cut-off Frequency GaN-based Schottky Diodes

High-power Schottky devices are widely used in various switching devices,and silicon-based devices are widely used in commercial applications,but silicon-based power devices perform poorly in high-frequency and high-power transmission and are difficult to satisfy.increasing demand for market demand.The second-generation semiconductors represented by GaAs have good characteristics at high frequencies,but the transMISsion power is too low,resulting in weak signals.The third-generation semiconductor GaN has good characteristics in power transmission and has a very good application development in high-frequency power devices.However,the mobility of GaN is significantly lower than that of GaAs,which leads to a large series resistance of GaN-based Schottky devices,making it difficult to increase the cutoff frequency of the device.The use of two-dimensional electron gas generated by an AlGaN/GaN heterojunction as a conductive layer can solve the problem of series resistance.By designing the original single-Al composition AlGaN layer as a gradient overlay of multiple AlGaN layers with different Al compositions.This method can well reduce the series resistance effect of the device,increase the operating frequency of the Schottky device,and enable the device to operate at a higher operating frequency,even a terahertz frequency operating environment.This article is divided into three parts in the research content,the first is to design a Schottky device with a single-layer heterojunction of planar structure and vertical structure,and calculate the series resistance of the Schottky device,the junction capacitance under zero bias,and the cutoff frequency.The maximum cut-off frequency is obtained by changing the size of the device anode.Followed by the design of multi-layer heterojunction Schottky device,in two aspects of planar structure and vertical structure.The multilayer heterojunction Schottky device compares a single heterojunction Schottky device in terms of device series resistance,junction capacitance under zero bias,and device cutoff frequency.Finally,a gradient aluminum composition multilayer heterojunction Schottky device is designed,with planar and vertical structures.The graded aluminum multilayer heterojunction Schottky device compares single-layer heterojunction Schottky devices by means of device series resistance,junction capacitance under zero bias,and device cut-off frequency.Find the Schottky structure that can increase the cutoff frequency,find better structure size parameters in the direction of reducing the series resistance and increasing the cutoff frequency of the device.In the structure of a Schottky diode device having a planar structure single-layer heterojunction single aluminum composition,a single Al-component AlGaN layer is designed as an aluminum composition graded-increased AlGaN layer.Different layers generate multilayer heterojunctions,multilayer heterojunctions can produce multilayered2DEGs,and multilayer 2DEGs form multiple layers of conductive channels that can reduce the polarization charge concentration of the channel.On the other hand,the width of the2DEG and the bandwidth of electron flow are broadened,which reduces the scattering of impurities and improves the mobility of electrons.The series resistance of the Schottky device of the device can be well reduced,and the cutoff frequency of the Schottky device can be increased.In the structure of a planar heterojunction Schottky device with a graded aluminum composition,the thickness of the Al_0.3Ga_0.7N layer and the thickness of the Al_0.2Ga_0.8N layer have a great influence on the series resistance,the junction capacitance of the bias voltage,and the cut-off frequency.In a gradient aluminum composition double heterojunction Schottky diode,when the thickness of the Al_0.3Ga_0.7N layer and the thickness of the Al_0.2Ga_0.8N layer are largely different,the thickness of the Al_0.3Ga_0.7N layer is much smaller than the thickness of the Al_0.2Ga_0.8N layer,then Schottky.The cutoff frequency of the device is the largest.