A systematic study of the nonselective and smooth etching of GaN/AIGaN het-erostructures was performed using C12/Ar/BCI3 inductively coupled plasmas (ICR).Nonselective etching can be realized by adjusting the BCI3 rat...A systematic study of the nonselective and smooth etching of GaN/AIGaN het-erostructures was performed using C12/Ar/BCI3 inductively coupled plasmas (ICR).Nonselective etching can be realized by adjusting the BCI3 ratio in the Cl2/Ar/BCI3 mixture (20%—60%), increasing the ICR power and dc bias, and decreasing the chamber pressure. Surface morphology of the etched heterostructures strongly depends on the gas chemistry and the chamber pressure. Specifically, with the addition of 20% BCI3 to Cl2/Ar (4:1) gas mixture, nonselective etching of GaN/Al0.28Ga0.72N heterostructures at high etch rate is maintained and the surface root-mean-square (rms) roughness is reduced from 10.622 to 0.495 nm, which is smoother than the as-grown sample. Auger electron spectroscopy (AES) analysis shows that the effective removal of residual oxygen from the surface of AIGaN during the etching process is crucial to the nonselective and smooth etching of GaN/AIGaN herterostructures at high etch rate.展开更多
A novel O2 plasma-based digital etching technology for p-GaN/AlGaN structures without any etch-stop layer was investigated using an inductively coupled plasma(ICP)etcher,with 100 W ICP power and 40 W rf bias power.Und...A novel O2 plasma-based digital etching technology for p-GaN/AlGaN structures without any etch-stop layer was investigated using an inductively coupled plasma(ICP)etcher,with 100 W ICP power and 40 W rf bias power.Under 40 sccm O2 flow and 3 min oxidation time,the p-GaN etch depth was 3.62 nm per circle.The surface roughness improved from 0.499 to 0.452 nm after digital etching,meaning that no observable damages were caused by this process.Compared to the dry etch only methods with Cl2/Ar/O2 or BCl3/SF6 plasma,this technique smoothed the surface and could efficiently control the etch depth due to its self-limiting characteristic.Furthermore,compared to other digital etching processes with an etch-stop layer,this approach was performed using ICP etcher and less demanding on the epitaxial growth.It was proved to be effective in precisely controlling p-GaN etch depth and surface damages required for high performance p-GaN gate high electron mobility transistors.展开更多
For the uracil-BX3 （X = F, Cl） systems, geometries and binding energies have been calculated by using the Lee-Young-Parr correlation functionals （B3LYP） method of density functional theory （DFT） and the second-o...For the uracil-BX3 （X = F, Cl） systems, geometries and binding energies have been calculated by using the Lee-Young-Parr correlation functionals （B3LYP） method of density functional theory （DFT） and the second-order Moller-Plesset （MP2） method of ab initio at the 6- 311 ＋G^＊ or 6-311 ＋＋G^＊ basis set. Four isomers were found for each system, and then the single-point energy evaluations were performed using the larger basis sets of （6-311 ＋G（2df, p） and aug-cc-pVDZ with DFF method. In the most stable isomer of uracil-BF3 or uracil-BCl3, the boron atom of BX3 （X = F, Cl） connects to the carbonyl oxygen O7 of uracil with a stabilization energy of -46.56 or -31.10 kJ/mol at the B3LYP/6-31 1＋G^＊ level （BSSE corrected）. The analyses for combining interaction between BX3 and uracil with the atom-in-molecule theory （AIM） and natural bond orbital method （NBO） have been performed. The results indicate that all isomers were formed with σ-p type interactions between uracil and BX3, in which the carbonyl oxygen offers its lone pair electrons to the empty p orbital of boron atom and the concomitances of charge transfer from uracil to BX3 occur. Moreover, there exists one or two hydrogen bonds in most isomers of uracil-BX3 system and these hydrogen bonds contribute to the stability of the complex systems. Frequency analysis suggests that the stretching vibration of BX3 undergoes a red shift in complexes. Uracil-BF3 complex is more stable than uracil-BCl3 although the distance of B-O is shorter in the latter. Besides, the conversion mechanisms between different isomers of uracil-BF3 have been obtained.展开更多
基金the Foundation for Key Projects of Basic Research (TG2000036601)the '863' High Tech Foundation (2002AA31119Z, 2001AA312190) the National Natural Science Foundation of China (Grant No. 60244001).
文摘A systematic study of the nonselective and smooth etching of GaN/AIGaN het-erostructures was performed using C12/Ar/BCI3 inductively coupled plasmas (ICR).Nonselective etching can be realized by adjusting the BCI3 ratio in the Cl2/Ar/BCI3 mixture (20%—60%), increasing the ICR power and dc bias, and decreasing the chamber pressure. Surface morphology of the etched heterostructures strongly depends on the gas chemistry and the chamber pressure. Specifically, with the addition of 20% BCI3 to Cl2/Ar (4:1) gas mixture, nonselective etching of GaN/Al0.28Ga0.72N heterostructures at high etch rate is maintained and the surface root-mean-square (rms) roughness is reduced from 10.622 to 0.495 nm, which is smoother than the as-grown sample. Auger electron spectroscopy (AES) analysis shows that the effective removal of residual oxygen from the surface of AIGaN during the etching process is crucial to the nonselective and smooth etching of GaN/AIGaN herterostructures at high etch rate.
基金Supported by the Guangdong Science and Technology Department(Grant Nos.2019B010128001 and 2019B010142001)the Shenzhen Municipal Council of Science and Innovation(Grant Nos.JCYJ20180305180619573 and JCYJ20170412153356899)the National Natural Science Foundation of China(Grant No.61704004)。
文摘A novel O2 plasma-based digital etching technology for p-GaN/AlGaN structures without any etch-stop layer was investigated using an inductively coupled plasma(ICP)etcher,with 100 W ICP power and 40 W rf bias power.Under 40 sccm O2 flow and 3 min oxidation time,the p-GaN etch depth was 3.62 nm per circle.The surface roughness improved from 0.499 to 0.452 nm after digital etching,meaning that no observable damages were caused by this process.Compared to the dry etch only methods with Cl2/Ar/O2 or BCl3/SF6 plasma,this technique smoothed the surface and could efficiently control the etch depth due to its self-limiting characteristic.Furthermore,compared to other digital etching processes with an etch-stop layer,this approach was performed using ICP etcher and less demanding on the epitaxial growth.It was proved to be effective in precisely controlling p-GaN etch depth and surface damages required for high performance p-GaN gate high electron mobility transistors.
基金This work was supported by the National Natural Science Foundation of China (No. 20171031)
文摘For the uracil-BX3 （X = F, Cl） systems, geometries and binding energies have been calculated by using the Lee-Young-Parr correlation functionals （B3LYP） method of density functional theory （DFT） and the second-order Moller-Plesset （MP2） method of ab initio at the 6- 311 ＋G^＊ or 6-311 ＋＋G^＊ basis set. Four isomers were found for each system, and then the single-point energy evaluations were performed using the larger basis sets of （6-311 ＋G（2df, p） and aug-cc-pVDZ with DFF method. In the most stable isomer of uracil-BF3 or uracil-BCl3, the boron atom of BX3 （X = F, Cl） connects to the carbonyl oxygen O7 of uracil with a stabilization energy of -46.56 or -31.10 kJ/mol at the B3LYP/6-31 1＋G^＊ level （BSSE corrected）. The analyses for combining interaction between BX3 and uracil with the atom-in-molecule theory （AIM） and natural bond orbital method （NBO） have been performed. The results indicate that all isomers were formed with σ-p type interactions between uracil and BX3, in which the carbonyl oxygen offers its lone pair electrons to the empty p orbital of boron atom and the concomitances of charge transfer from uracil to BX3 occur. Moreover, there exists one or two hydrogen bonds in most isomers of uracil-BX3 system and these hydrogen bonds contribute to the stability of the complex systems. Frequency analysis suggests that the stretching vibration of BX3 undergoes a red shift in complexes. Uracil-BF3 complex is more stable than uracil-BCl3 although the distance of B-O is shorter in the latter. Besides, the conversion mechanisms between different isomers of uracil-BF3 have been obtained.
