Nitrides with Nonpolar Surfaces
Nitrides with Nonpolar Surfaces
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具有非极性表面的氮化物
DOI：
10.1002/9783527623150
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发表时间：
2008
期刊：
影响因子：
8.8
通讯作者：
T. Paskova
中科院分区：
文献类型：
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作者：
T. Paskova
晶体缺陷，例如点缺陷、线缺陷、平面缺陷和体积缺陷是半导体在微电子中的适用性的限制因素。这些缺陷对能带结构、载流子迁移率和光学性质的影响甚至被发现对某些材料的适用性产生主要障碍。一个例子是II-VI材料系统，其中一个突出的障碍是在器件操作期间产生扩展缺陷，与掺杂相关的点缺陷的扩散有关[1]，导致寿命缩短并使器件不可靠。相比之下，III族氮化物化合物的质量在过去几年中得到了极大的改善，使得它们可用于可靠的光电器件，例如发光二极管或激光二极管。然而，由于量子阱区中电子和空穴波函数的重叠减少，由Ga和N之间的电荷分离引起的用于极性c平面取向生长的强自发极化场导致这种器件的量子效率显著降低[2]。这激发了对具有非极性生长平面的氮化物基薄膜的生长方法的研究。例如，沿着[11 20]轴的生长导致在生长方向[3，4]上具有零自发极化场的膜，并且可以在蓝宝石衬底上实现，蓝宝石衬底是目前市场上可获得的最便宜的衬底。尽管早在1987年就进行了在r面蓝宝石上非极性GaN膜的第一沉积实验[5]，但是在过去主要研究纤锌矿GaN和相关化合物中的缺陷结构，重点关注沿着六方[0001]轴（c轴）取向的膜。诸如分子束外延（MBE）[1]、金属有机气相外延（MOVPE）[6]和氢化物气相外延（HVPE）[7，8]的生长技术被建立用于极性以及非极性GaN生长。a面GaN的结构质量
Crystal imperfections, such as point defects, line defects, planar and volume defects are limiting factors for the applicability of semiconductors in microelectronics. The impact of these defects on band structure, carrier mobility, and optical properties is even found to create principal obstacles for the applicability of certain materials. One example is the II-VI material system for which a prominent obstacle is the creation of extended defects during device operation, connected with the diffusion of doping-related point defects [1], causing lifetime shortening and making the device unreliable. In contrast, the quality of group III nitride compounds has been improved tremendously in the past years, so that they became applicable for reliable optoelectronic devices such as light-emitting diodes or laser diodes. However, the strong spontaneous polarization field caused by the charge separation between the Ga and the N for polar c-plane oriented growth leads to a significant reduction of the quantum efficiency of such devices owing to a reduced overlap of the electron and hole wave-functions in the quantum well region [2]. This motivates the research of approaches for the growth of nitridebased films having a nonpolar growth plane. For example, the growth along the [11 20] axis results in films with zero spontaneous polarization field in growth direction [3, 4] and can be realized on sapphire substrates, which are currently the least expensive substrates available in the market. Although first deposition experiments of nonpolar GaN films on r-plane sapphire were performed as early as in 1987 [5], the defect structure in wurtzite GaN and related compounds has been mainly studied in the past focusing on films oriented along the hexagonal [0001] axis (c-axis). Growth techniques such as molecular beam epitaxy (MBE)[1], metal organic vapor phase epitaxy (MOVPE)[6], and hydride vapor phase epitaxy (HVPE)[7, 8] are established for polar as well as nonpolar GaN growth. The structural quality of a-plane GaN