New Structures And Switching Characteristics Of AlGaN/GaN HEMT Devices

As a leader of the third generation semiconductors-Gallium nitride?GaN?with superior material properties,becoming the research hotspot both at home and abroad,is widely used in the field of power electronics.With further research on GaN power devices,many problems are gradually exposed.For example,the voltage blocking ability of GaN power device is far from the theoretical limit and the delay as a switching device has not been fully answered.To solve the problems above,this paper has carried out a profound study.Firstly,techniques to improve the breakdown voltage of GaN power devices are illustrated briefly,including the innovative process and structures,etc.what's more,the voltage blocking mechanism and the existing problems are analyzed similarly.Then several leakage current and general breakdown mechanisms of GaN power devices are summarized,and made a series of analyses and exploration in the following section.Finally,the current status of GaN power devices as switch is introduced and the influence factors of switching characteristics are briefly analyzed and illustrated.On the basis of the above,a high breakdown voltage GaN-on-Insulator based heterojunction field effect transistor with a partial back barrier?PB-GOI HFET?is proposed in this paper.Because of the spontaneous polarization intensity of AlGaN is larger than GaN,several negative charges will be induced along the interface of GaN/Al_xGa_1-xN PB barrier.These negative charges can partly deplete the 2DEG induced in Gate-Drain drift region,forming a structure of low density drain,which can make the breakdown voltage improved significantly by modulating the distribution of electric field along the channel.Compared with a conventional GOI HFET,the proposed PB-GOI HFET with gate–drain distance of 5?m possesses the breakdown voltage of 1200 V and the FOM of 3.12 GW/cm2,which increased by more than 353%and 976%.PB-GOI HFET can not only maintain the original advantages of GOI structure,but also improve the breakdown voltage without degradation of frequency performance.The novel PB-GOI HFET shows great prospects for power electronics applications.Finally,distinct from the static characteristics discussed above,then the study focused on the analysis of switching characteristics.Firstly,analyzing the disadvantages of current simulation methods in this section and studying the MixedMode simulation method of the device simulation tool-Silvaco and the circuit simulation tool-Spice comprehensively.Secondly,the present technology and the advantages and disadvantages of the implementation of E-mode devices are briefly introduced.Meanwhile,the basic characteristics include output,transfer and breakdown of P-GaN power device are illustrated in detail.Then the switching characteristics of P-GaN power device are discussed by the MixedMode simulation method introduced above and the influence factors of switching characteristics are emphasized.