Investigation of high density two-dimensional electron gas in Zn-polar BeMgZnO/ZnO heterostructures
Investigation of high density two-dimensional electron gas in Zn-polar BeMgZnO/ZnO heterostructures
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DOI：
10.1063/1.4993853
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发表时间：
2017-10-30
影响因子：
4
通讯作者：
Morkoc, H.
中科院分区：
文献类型：
--
作者：
Ding, K.;Ullah, M. B.;Morkoc, H.
采用分子束外延技术在高阻GaN模板上生长了Zn极性的BeMgZnO/ZnO异质结构，并产生了高密度的二维电子气。这是出于需要达到等离子体-纵向光学（LO）声子共振以获得最小LO声子寿命。在MgZnO/ZnO异质结构中实现高2DEG浓度需要在相对低的温度下生长MgZnO阻挡层，这损害了三元质量，这又阻碍了势场效应晶体管性能。当这种三元合金进一步与BeO，应变的迹象BeMgZnO的障碍，ZnO开关从压缩到拉伸，使压电和自发极化是添加剂的BeMgZnO/ZnO异质结构非常像的Ga极性AlGaN/GaN异质结构。结果，在Be0.03Mg0.41Zn0.56O/ZnO异质结构中实现了1.2 × 10（13）cm（-2）的2DEG浓度。为了比较，7.7 × 10（12）cm（-2）的2DEG浓度需要在阻挡层中具有2%的Be和26%的Mg，而在MgZnO/ZnO系统中同样需要将超过40%的Mg结合到阻挡层中，这需要非常低的生长温度。我们的结果是一致的要求，实现短的LO声子寿命，通过等离子体激元LO声子共振高载流子速度。出版社：AIP Publishing
Zn-polar BeMgZnO/ZnO heterostructures grown by molecular beam epitaxy on high resistivity GaN templates producing high-density two-dimensional electron gas (2DEG) are investigated. This is motivated by the need to reach plasmon-longitudinal optical (LO) phonon resonance for attaining minimum LO phonon lifetime. Achievement of high 2DEG concentration in MgZnO/ZnO heterostructures requires growth of the MgZnO barrier at relatively low temperatures, which compromises the ternary quality that in turn hinders potential field effect transistor performance. When this ternary is alloyed further with BeO, the sign of strain in the BeMgZnO barrier on ZnO switches from compressive to tensile, making the piezoelectric and spontaneous polarizations to be additive in the BeMgZnO/ZnO heterostructures much like the Ga-polar AlGaN/GaN heterostructures. As a result, a 2DEG concentration of 1.2 x 10(13) cm(-2) is achieved in the Be0.03Mg0.41Zn0.56O/ZnO heterostructure. For comparison, a 2DEG concentration of 7.7 x 10(12) cm(-2) requires 2% Be and 26% Mg in the barrier, whereas the same in the MgZnO/ZnO system would require incorporation of more than 40% Mg into the barrier, which necessitates very low growth temperatures. Our results are consistent with the demands on achieving short LO phonon lifetimes through plasmon-LO phonon resonance for high carrier velocity. Published by AIP Publishing.