Researches On Oxygen Treatment Of Hydrogen-termined Diamond And Stability Of Diamond Field Effect Transistors

Diamond has excellent properties such as wide band gap,high breakdown voltage,high electron hole mobility,low dielectric constant and superhardness,high thermal conductivity,radiation resistance,and good chemical stability.It is used in electronic power devices,ultraviolet light emitting diodes,solid-state spin quantum devices have an irreplaceable role in other materials.As a third-generation semiconductor material,diamond has made important progress in the basic and applied research of semiconductor devices.The key issue in achieving diamond in semiconductor devices is to obtain high-performance p-type and n-type doping.At present,the shallow donor level n-type Doping is still a challenging problem.Although the boron-doped p-type diamond acceptor energy level is shallow??0.37eV?,it is still not suitable for device applications at normal temperature.The hydrogen terminated diamond surface has p-type semiconductor characteristics,which can form two dimensional hole gas?2DHG?with extremely low activation energy.It has been applied to the make of high performance diamond field effect transistor?FET?devices.In order to improve the performance of diamond-based semiconductor devices,there are many topics that need to be studied in depth in terms of hydrogen terminal diamond surface conductance and related device properties.1.During the oxidation treatment of the hydrogen terminated diamond surface with UV/ozone,the UV/ozone treatment time was changed to modulate the oxygen adsorption concentration,wettability,and conductive properties of the hydrogen-terminated diamond surface.According to X-ray photoelectron spectroscopy?XPS?analysis,as the UV/ozone treatment time increases,more oxygen?O?atoms are chemically adsorbed to replace the surface hydrogen?H?atoms,changing the surface of the diamond single crystal H/O terminal status.Considering the intrinsic properties of diamond?hydrogen terminal hydrophobicity,oxygen-terminal hydrophilicity?and single crystal smooth surface,the relationship between wettability and UV/ozone treatment time is related to the change in surface O adsorption ratio,which is consistent with XPS analysis results.The Hall effect measurement results show that the resistance of the hydrogen-terminated diamond single crystal?hole mobility?increases with UV/ozone treatment time,and the surface resistance?mobility?increases?decreases?,which is consistent with the XPS and wettability changes.It is proved that by changing the ultraviolet/ozone treatment time?minutes or seconds?,changing the ratio of hydrogen and oxygen terminal concentrations on diamond surface,regulating the wettability and electric transport properties of diamond surface,providing important reference data for surface functionalization and electrical properties regulation of diamond based electronic devices.2.By scanning the gate voltage in different directions during the current-voltage?I-V?characteristic measurement,the stability study of hydrogen terminated diamond based MOSFET device?the gate insulation medium of this structure is low temperature atomic layer deposition of aluminum oxide,ALD-Al₂O₃?was carried out.Drain current density(I_ds)and drain voltage(V_ds)characteristics of hydrogen terminal diamond MOSFET devices were measured under two changes of gate voltage from reverse to forward?RF?and forward to reverse?FR?.For gate scanning in RF and FR directions,Ids are different at the same voltage.Hysteresis was observed during the scan.When fixed drain voltage V_ds=-6V,the threshold voltage of scanning in different directions is different,RF direction V_th=16.4V,FR direction V_th=15.1V.The measurement results of the gate leakage current in the scanning directions of RF and FR show that the leakage current is extremely low at low gate voltage,and the scanning in the FR direction can reduce the gate leakage,indicating that the ALD-Al₂O₃ layer has good insulation.At low drain voltage,the subthreshold swing?SS?value changes little,while at higher drain voltage,the SS value increases.At higher drain voltages,the device channel cannot be completely pinched off,the transconductance?g_m?increases as the drain voltage increases,and the g_m is the largest in the RF direction.For the hysteresis of transfer characteristics during the scanning in the RF and FR directions,the drain current density was measured with time after applying the gate bias,due to the deep-level charge trap near the ALD-Al₂O₃ boundary near the hydrogen terminated corundum surface.This leads to instability of the hydrogen terminated diamond MOSFET.3.The performance of the diamond metal-semiconductor field effect transistor?MESFET?on the hydrogen terminal surface under X-ray radiation was studied.Before and after X-ray radiation,the drain current density of the device changed slightly,and the transconductance?gm?after radiation was significantly smaller than the gm before radiation.On the one hand,it illustrates the anti-radiation characteristics of diamond-based semiconductor devices.On the other hand,under the effect of a certain radiation intensity,it is found that radiation-induced hydrogen-end diamond produces hole electron pairs,which are accelerated in the electric field,and high-energy holes will bombard the gate.The C-H bond causes hydrogen to transfer to the interface to form an interface trap state,and the performance of the device changes before and after using radiation.This result provides important experimental data for in depth analysis of the effect of reducing X-ray radiation on the performance of diamond MESFET devices.Diamond is regarded as one of the most important third-generation semiconductor materials.The performance of diamond-based devices is closely related to the structure and properties of the surface and interface.This paper has done a series of work on the hydrogen terminal diamond surface oxygen terminal treatment,MOSFET device stability test and MESFET device X-ray radiation resistance,etc.The results are for in-depth analysis of the structure and performance of diamond materials and devices in various environmental atmospheres Changes,solve the related problems encountered in the application of diamond devices,design and manufacture new diamond based semiconductor devices,provide experimental data and program ideas.