AlGaN插入层对InAlN/AlGaN/GaN异质结散射机制的影响
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摘要
InAlN/AlN/GaN异质结中,名义上的AlN插入层实为Ga含量很高的AlGaN层, Al, Ga摩尔百分比决定了电子波函数与隧穿几率,因此影响与InAlN/AlGaN势垒层有关的散射机制.本文通过求解薛定谔-泊松方程与输运方程,研究了AlGaN层Al摩尔百分含量对InAlN组分不均匀导致的子带能级波动散射、导带波动散射以及合金无序散射三种散射机制的影响.结果显示:当Al含量由0增大到1,子带能级波动散射强度与合金无序散射强度先增大后减小,导带波动散射强度单调减小;在Al含量为0.1附近的小组分范围内,合金无序散射是限制迁移率的主要散射机制,该组分范围之外,子带能级波动散射是限制迁移率的主要散射机制;当Al摩尔百分含量超过0.52,三种散射机制共同限制的迁移率超过无插入层结构的迁移率, AlGaN层显示出对迁移率的提升作用.
Recent studies showed that the nominal AlN interlayers in InAlN/AlN/GaN heterostructures had high GaN mole fractions, especially those grown by metalorganic chemical vapor deposition. The Al and Ga mole fraction in the AlGaN interlayer determine the electron wave function and penetration probability, and thus affecting the scattering mechanism related to the InAlN/AlGaN potential layers. In this paper we study the effects of Al mole fraction of the AlGaN interlayer on three scattering mechanisms related to the potential layer, i.e. alloy disorder scattering, subband energy fluctuation scattering and conduction band fluctuation scattering induced by In compositionally inhomogeneous InAlN layer. The wave function and penetration probability in the InAlN/AlGaN/GaN heterostructure are determined by self-consistently calculating the Schr?dinger-Poisson equations and then used to calculate the scattering mechanisms. The results show that penetration probabilities in the InAlN and AlGaN both decrease with increasing Al mole fraction. The combination of the contribution of the screening effect and the two-dimensional electron gas(2DEG) density inhomogeneity results in an initial decrease and subsequent increase in the subband energy fluctuation scattering-limited mobility with increasing Al mole fraction, and the heterostructure with a smaller InAlN thickness has a larger mobility increase. The penetration probability and non-periodic arrangement of Al and Ga in the AlGaN predict an Al mole fraction dependence of the alloy disorder scattering-limited mobility similar to the subband energy fluctuation scattering-limited mobility, and the alloy disorder scattering occurs mainly in the AlGaN because the penetration probability in the AlGaN is much higher than in the InAlN. The conduction band fluctuation scattering-limited mobility monotonically increases with increasing Al mole fraction due to the decrease of the penetration probability. The subband energy fluctuation scattering-limited mobility is less sensitive to variation in the Al mole fraction than the other two scattering mechanisms-limited mobilities.In a small Al mole fraction range around 0.1, the alloy disorder scattering is a dominant scattering mechanism, while the subband energy fluctuation scattering dominates the mobility beyond this compositional range. When Al mole fraction is above 0.52, the three scattering mechanisms-limited mobility exceeds that in the InAlN/GaN heterostructure without the AlGaN interlayer, indicating the promotion of the mobility by the AlGaN interlayer. The mobility is raised by more than 50 percent in the InAlN/AlN/GaN heterostructure with an AlN interlayer compared with that in the InAlN/GaN heterostructure without the interlayer.
Recent studies showed that the nominal AlN interlayers in InAlN/AlN/GaN heterostructures had high GaN mole fractions, especially those grown by metalorganic chemical vapor deposition. The Al and Ga mole fraction in the AlGaN interlayer determine the electron wave function and penetration probability, and thus affecting the scattering mechanism related to the InAlN/AlGaN potential layers. In this paper we study the effects of Al mole fraction of the AlGaN interlayer on three scattering mechanisms related to the potential layer, i.e. alloy disorder scattering, subband energy fluctuation scattering and conduction band fluctuation scattering induced by In compositionally inhomogeneous InAlN layer. The wave function and penetration probability in the InAlN/AlGaN/GaN heterostructure are determined by self-consistently calculating the Schr?dinger-Poisson equations and then used to calculate the scattering mechanisms. The results show that penetration probabilities in the InAlN and AlGaN both decrease with increasing Al mole fraction. The combination of the contribution of the screening effect and the two-dimensional electron gas(2DEG) density inhomogeneity results in an initial decrease and subsequent increase in the subband energy fluctuation scattering-limited mobility with increasing Al mole fraction, and the heterostructure with a smaller InAlN thickness has a larger mobility increase. The penetration probability and non-periodic arrangement of Al and Ga in the AlGaN predict an Al mole fraction dependence of the alloy disorder scattering-limited mobility similar to the subband energy fluctuation scattering-limited mobility, and the alloy disorder scattering occurs mainly in the AlGaN because the penetration probability in the AlGaN is much higher than in the InAlN. The conduction band fluctuation scattering-limited mobility monotonically increases with increasing Al mole fraction due to the decrease of the penetration probability. The subband energy fluctuation scattering-limited mobility is less sensitive to variation in the Al mole fraction than the other two scattering mechanisms-limited mobilities.In a small Al mole fraction range around 0.1, the alloy disorder scattering is a dominant scattering mechanism, while the subband energy fluctuation scattering dominates the mobility beyond this compositional range. When Al mole fraction is above 0.52, the three scattering mechanisms-limited mobility exceeds that in the InAlN/GaN heterostructure without the AlGaN interlayer, indicating the promotion of the mobility by the AlGaN interlayer. The mobility is raised by more than 50 percent in the InAlN/AlN/GaN heterostructure with an AlN interlayer compared with that in the InAlN/GaN heterostructure without the interlayer.
引文
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[2]Xue J S,Zhang J C,Hou Y W,Zhou H,Zhang J F,Hao Y 2012 Appl.Phys.Lett.100 013507
[3]Shen B,Tang N,Yang X L,Wang M J,Xu F J,Wang X Q,Qin Z X 2017 Prog.Phys.37 81(in Chinese)[沈波,唐宁,杨学林,王茂俊,许福军,王新强,秦志新2017物理学进展37 81]
[4]Kaun S W,Ahmadi E,Mazumder B,Wu F,Kyle E CH,Burke P G,Mishra U K,Speck J S 2014 Semicond.Sci.Technol.29 045011
[5]Higashiwaki M,Chowdhury S,Miao M S,Swenson B L,van der Walle C G,Mishra U K 2010 J.Appl.Phys.108063719
[6]Hao Y,Xue J S,Zhang J C 2012 Sci.China Ser.F 421577(in Chinese)[郝跃,薛军帅,张进成2012中国科学:信息科学42 1577]
[7]Fang Y L,Feng Z H,Yin J Y,Zhang Z R,LüY J,Dun S B,Liu B,Li C M,Cai S J 2015 Phys.Status Solidi B252 1006
[8]Ahmadi E,Chalabi H,Kaun S W,Shivaraman R,Speck J S,Mishra U K 2014 J.Appl.Phys.116 133702
[9]Li Q,Chen Q,Chong J 2017 AIP Adv.7 125103
[10]Wang P Y,Zhang J F,Xue J S,Zhou Y B,Zhang J C,Hao Y 2011 Acta Phys.Sin.60 117304(in Chinese)[王平亚,张金风,薛军帅,周勇波,张进成,郝跃2011物理学报60 117304]
[11]Ni J Y,Hao Y,Zhang J C,Duan H T,Zhang J F 2009Acta Phys.Sin.58 4925(in Chinese)[倪金玉,郝跃,张进成,段焕涛,张金风2009物理学报58 4925]
[12]Yang P,LüY W,Wang X B 2015 Acta Phys.Sin.64197303(in Chinese)[杨鹏,吕燕伍,王鑫波2015物理学报64 197303]
[13]Mazumder B,Kaun S W,Lu J,Keller S,Mishra U K,Speck J S 2013 Appl.Phys.Lett.102 111603
[14]Sridhara Rao D V,Jain A,Lamba S,Muraleedharan K,Muralidharan R 2013 Appl.Phys.Lett.102 191604
[15]Ambacher O,Foutz B,Smart J,Shealy J R,Weimann N G,Chu K,Murphy M,Sierakowski A J,Schaff W J,Eastman L F 2000 J.Appl.Phys.87 334
[16]Jiao W,Kong W,Li J,Collar K,Kim T H,Losurdo M,Brown A S 2016 Appl.Phys.Lett.109 082103
[17]Li Q,Chen Q,Chong J 2018 Acta Phys.Sin.67 027303(in Chinese)[李群,陈谦,种景2018物理学报67 027303]
[18]Li Q,Zhang J W,Zhang Z Y,Li F N,Hou X 2014Semicond.Sci.Technol.29 115001
[19]Quang D N,Tung N H,Tuoc V N,Minh N V,Huy HA,Hien D T 2006 Phys.Rev.B 74 205312
[20]Hao Y,Zhang J F,Zhang J C 2013 Nitride Wide Bandgap Semiconductor Material and Electronic Devices(Beijing:Science Press)p8(in Chinese)[郝跃,张金风,张进成2013氮化物宽禁带半导体材料与电子器件(北京:科学出版社)第8页]
[21]Lee K S,Yoon D H,Bae S B,Park M R,Kim G H 2002ETRI J.24 270