Fabracation And Performance Research Of β-Ga₂O₃ Pn Junction

As third-generation semiconductor material,gallium oxide（Ga₂O₃）has the characteristics of large forbidden band width,high breakdown field strength.These properties are superior to the traditional third-generation semiconductor materials,such as Si C,Ga N.At present,the development of gallium oxide Schottky diodes has reached the limit of gallium oxide materials.In view of the lack of p-type materials of gallium oxide materials,if we want to achieve the high-power devices of higher power,stronger heat dissipation,and more stable,heterojunction devices of n-typeβ-Ga₂O₃and other p-type materials with excellent composition properties are new research directions.The main research contents and results of this article are as follows:First,based on the fabrication of n-β-Ga₂O₃/p-Ga N heterojunction diodes,the effect of Ar plasma treatment on the ohmic characteristics ofβ-Ga₂O₃ was investigated.Ar plasma treatment reduced the contact resistance of the TLM pattern from 4.67Ω·mm to 2.01Ω·mm,which was reduced to 43%without treatment.The film sheet resistance(R_SH)of the TLM was reduced from 1.71 kΩ/□without treatment to 1.68 kΩ/□.Ar plasma treatment can stimulate the generation of oxygen vacancies on the surface ofβ-Ga₂O₃.As a result,the electron concentration on the surface ofβ-Ga₂O₃has been increased and the Ti/Au ohmic contact ofβ-Ga₂O₃ has been significantly improved.Secondly,the conduction mechanism of n-β-Ga₂O₃/p-Ga N heterojunction diodes has been studied.n-β-Ga₂O₃/p-Ga N heterojunction devices using gallium oxide mechanical exfoliate and transfer technology have been successfully fabricated.After a comprehensive test,the following have been concluded.The built-in potential（V_D）is 3.4 V.The electron concentration of n-typeβ-Ga₂O₃ is 2.9×10¹⁷cm^-3 and the effective hole concentration of p-type Ga N is 1.3×10¹⁷cm^-3.The space charge region widths on both sides of the heterojunction are 1.34μm and 0.60μm,respectively,and the built-in potentials are 2.36 e V and 0.95 e V and the device band diagram has been constructed.The interface state density(D_it)of the device is estimated to 2.3～5.3×10¹³e V^-1cm^-2 using high-low frequency(C_LF-C_HF)method.At room temperature,the current switching ratio is 10⁶ at the voltage bias of±20 V,and the turn-on voltage is 3.9 to 4.3 V.The device has excellent rectification characteristics.The forward current of the device can be divided into three regions corresponding to three types of current transport mechanisms:the compound-tunneling mechanism(region I:10^-7A?I?10^-4A),the trapped charge-limited space charge-limited current(region II:10^-7A?I?10^-4A)and the space charge limiting current（SCLC）of a single carrier（electron）(region III:I>10^-4A).Exponential distribution of traps in region II shows the device exhibits different trap charge activation energies and trap charge concentrations in the low temperature range（25 ^oC-75 ^oC）and high temperature range（87.5^oC-150 ^oC）,which are 0.113 e V,1.63×10¹⁶cm^-3and 0.109 e V,1.71×10¹⁶ cm^-3.The reverse current of the device is the space charge limited current limited by the trap charge.The exponentially distributed trap charge concentration is determined to be 1.73×10¹⁷ cm^-3.The reverse current conduction mechanism is consistent with the forward characteristic in region II.Space charge limiting current plays an important role in the current conduction of the device,and the effect of trap charge on the reverse characteristics of the device is more significant.Third,a protective layer of 50 nm-thick alumina was used to optimized the process.The effect of supercritical carbon dioxide（SCCO₂）treatment has been investigated.For the forward characteristics of the device,SCCO₂ treatment did not change the conductive mechanism of the device and it has little impact on device performance.However,SCCO₂treatment reduced the ideal factor of the device from 4.35 to 3.18,and the proportion of the device’s tunneling current decreased,which significantly inhibited the device’s interface traps,but the SCCO₂ treatment did not change the device’s conduction mechanism.For the reverse characteristics of the device,SCCO₂ treatment increased the device breakdown voltage to-134.8 V,which is 89%higher than the untreated device（-71.4 V）.It can be proved that SCCO₂ treatment can carry H₂O molecules to reach the interface of heterojunction,so that the dangling bond of gallium（Ga-）at the heterojunction interface combines with the hydroxy（-OH）in water,which can reduce the number of dangling bonds at the heterojunction interface and improve the reverse characteristic.