不同晶面的氢终端单晶金刚石场效应晶体管特性

通过微波等离子体化学气相淀积技术生长单晶金刚石并切割得到(110)和(111)晶面金刚石片,以同批器件工艺制备两种晶面上栅长为6μm的氢终端单晶金刚石场效应管,从材料和器件特性两方面对两种晶面金刚石进行对比分析.(110)面和(111)面金刚石的表面形貌在氢终端处理后显著不同,光学性质则彼此相似.VGS=–4 V时,(111)金刚石器件获得的最大饱和电流为80.41 m A/mm,约为(110)金刚石器件的1.4倍;其导通电阻为48.51 W·mm,只有(110)金刚石器件导通电阻的67%.通过对器件电容-电压特性曲线的分析得到,(111)金刚石器件沟道中最大载流子密度与(110)金刚石器件差异不大.分析认为,(111)金刚石器件获得更高饱和电流和更低导通电阻,应归因于较低的方阻.

Characteristics of hydrogen-terminated single crystalline diamond field effect transistors with different surface orientations

Diamond has great potential applications in high-power,high-frequency semiconductor devices because of its wide band gap(5.5 e V),high thermal conductivity(22 W/(cm·K)),and high carrier mobility(4500 cm2/(V·s)for electron,and 3800 cm2/(V·s)for hole).It has been widely considered as an ultimate semiconductor.From the analysis of our previous work,we find that the output current of field effect transistor based on hydrogenterminated polycrystalline diamond is usually larger than that based on single crystal diamond,and that the preferential orientations of the polycrystalline diamond are mainly(110)and(111)shown by XRD results.Therefore,in order to further analyze the effect of surface orientation on the device performance of hydrogenterminated diamond field effect transistor(FET),we study the devices fabricated respectively on the(110)plane and(111)plane single crystal diamond plates obtained from a single 3.5-mm-thick single crystal diamond grown by the microwave plasma chemical vapor deposition on the high-pressure high-temperature synthesized diamond substrate.Prior to processing the device,these diamond plates are characterized by atomic force microscope,Raman spectra and photoluminescence(PL)spectra.The results of Raman and PL spectra show that(110)plane and(111)plane plates originating from the same CVD single crystal diamond have no significant difference in optical property.Then the normally-on hydrogen-terminated diamond FET with a gate length of 6μm is achieved.The device on(111)plane delivers a saturation drain current of 80.41 m A/mm at a gate voltage VGS=–4 V,which is approximately 1.4 times that of the device on(110)plane.Meanwhile,the on-resistance of the device on(111)plane is 48.51 W·mm,and it is only 67%of the device on(110)plane.Analyses of the capacitance-voltage show that the hole concentration of the gated device on(110)plane and(111)plane are 1.34×1013 cm–2 and 1.45×1013 cm–2,respectively,approximately at the same level.In addition,the hole density of the device on both(110)and(111)plane increase near-linearly with the increase of gate voltage from the threshold voltage to–4 V,indicating that the control effect of the gate on the carrier in the channel is uniform.The possible reason for the higher saturation drain current as well as the lower onresistance of the device on(111)plane is that its sheet resistance is lower.