Crystal-orientation effects on the piezoelectric field and electronic properties of strained wurtzite semiconductors
Crystal-orientation effects on the piezoelectric field and electronic properties of strained wurtzite semiconductors
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DOI：
10.1103/physrevb.59.4725
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发表时间：
1999-02-15
影响因子：
3.7
通讯作者：
Chuang, SL
中科院分区：
文献类型：
--
作者：
Park, SH;Chuang, SL
研究了晶体取向对应变 GaN 体半导体的压电场和电子特性的影响。显示了使用最近导出的块对角化哈密顿量的应变纤锌矿 GaN 的带隙、波函数和动量矩阵元素的解析表达式。我们发现顶部两个价带之间的能量分离随着生长 (z') 方向与 c 轴之间的角度 theta 的增加而增加。对于压缩应变和拉伸应变的 GaN 晶体，这会导致顶价带沿横向 (k(x)') 方向的有效质量随着角度的增加而显着减少。在量子阱（QW）结构的价带色散关系中观察到类似的结果。 QW 结构的色散曲线还显示，由于压电场，克莱默简并性有所提升，从而导致电势不对称。我们发现，对于θ大于或等于30度的生长方向，压应变GaN的导带（C）和重空穴（HH）带之间的TE偏振的光学矩阵元大约是（0001）取向（theta=0度）的两倍大。将压缩应变和拉伸应变的压电极化绘制为生长方向的函数。出现最大极化时的晶体取向显示为应变的函数。特别地，沿着(10 (1) over bar 0)生长方向(theta=90度)的GaN晶体对于压缩应变和拉伸应变表现出零法向压电极化(P-z')。这些结果表明，压电场和应变的晶体取向依赖性显着影响电子传输特性以及光学带间吸收特性。 [S0163-1829(99)03008-8]。
Crystal orientation effects on the piezoelectric field and electronic properties of strained GaN bulk semiconductors are investigated. Analytical expressions for the band gap, wave function, and momentum matrix element of strained wurtzite GaN using a recently derived block-diagonalized Hamiltonian are shown. We find that the energy separation between the top two valence bands increases with the angle theta between the growth (z') direction and the c axis. This results in a significant reduction of the effective mass of the top valence band along the transverse (k(x)') direction with increasing angle for both compressively and tensilely strained GaN crystals. Similar results are observed in the valence-band dispersion relations for the quantum-well (QW) structure. The dispersion curves for the QW structure also show a lifting of the Kramers degeneracy due to the piezoelectric field, which causes an asymmetry in the potential. We find that the optical matrix element of the TE polarization between the conduction (C) and heavy hole (HH) bands of the compressively strained GaN for a growth direction with theta greater than or equal to 30 degrees is about twice as large as that of the (0001) orientation (theta=0 degrees). The piezoelectric polarizations of the compressive and tensile strains are plotted as a function of the growth direction. The crystal orientation at which a maximum polarization occurs is shown as a function of strain. In particular, the GaN crystal along the (10 (1) over bar 0) growth direction (theta=90 degrees) shows zero normal piezoelectric polarization (P-z') for the compressive and tensile strains. These results show that crystal orientation dependence of the piezoelectric field and strain significantly affect the electronic transport properties as well as optical interband absorption properties. [S0163-1829(99)03008-8].