Sub-Atomic-Layr Epitaxy of Si/Ge Semiconductors

原子层外延（ALE）是一种利用单层饱和吸附反应逐层生长薄膜的外延膜生长技术；一个自限函数。氢化物分子因不含杂质而具有吸引力。然而，由于氢化物分子的饱和覆盖范围小于单层，通常难以利用氢化物分子实现ALE。1993年，Suda（首席研究员）等人提出了一种亚原子层外延（SALE）方法，该方法通过亚单层重复暴露氢化物分子和表面热激发诱导的吸附原子迁移过程，在亚单层下外延生长薄膜。结合原子迁移过程是ALE的一个尚未被关注的关键过程，利用它可以实现亚单层的亚单层外延。本研究在Si_<>H_6-on-Si（001）体系中得到了SALE生长条件与生长方式、生长速率和生长形态的关系。在此基础上，提出了一个销售增长模型。通过这些工作，获得了销售的基本增长机制和增长控制方法。结果表明，当氢化物分子的饱和覆盖范围在0 ~ 2个单层时，SALE生长以饱和覆盖为生长单位。在本研究中，还研究了一种Si/Ge ALE的方法。通过这项工作，首次应用了热裂解方法，并发现热裂解的Si_<>H_6物质在Si（001）和Ge（001）上均在单分子层上饱和。对于GE（001）上的Si ALE， Si/ GE界面是突变的。结果表明，热裂解的GeH_4也很有希望用于Ge ALE。随着首席研究员提出的利用氢化物分子的SALE和热裂解ALE， iv族半导体的原子控制外延技术有望得到广泛推广，该方法将为Si/Ge量子阱器件的发展做出巨大贡献。少

Atomic Layr Epitaxy (ALE) is an epitaxial film growth technique with which a film is grown layr-by-layr using an one-monolayr saturation adsorption reaction ; a self -limiting function. Hydride molecules are attractive for their being free of impurity species. However, since their saturation coverages are less than one monolayr, it is generally difficcult to realize ALE using the hydride molecules. In 1993, Suda (head investigator) et al. proposed that a sub-atomic-layr epitaxy (SALE) method with which a film is epitaxially grown submonolayr by submonolayr repeating an exposure of hydride molecules and an adatom migration process induced by surface thermal excitation. The adatom migration process is a key process which has not been focused on for ALE and with it, submonolayr-by submonolayr epitaxy is relized. In this research, the relationship between the SALE prowth conditions and growth characteristics including growth modes, growth rates, and growth morphologies has been obtained us … More ing a Si_<>H_6-on-Si (001) system. On the basis of the results, a SALE growth model has been proposed Through these work, fundamental growth mechanisms and a growth control method for SALE has been obtained. The results suggest that SALE growth with a growth unit of saturation coverage if the saturation coverage of a hydride molecule is in the rangeof 0 to 2 monolayr. In this resesarch, a method for Si/Ge ALE has been also investigated. Through this work, thermally cracking method was first applied and it has been found that thermally cracked Si_<>H_6 species saturate at one monolayr on both Si (001) and Ge (001). In the case of Si ALE on GE (001), Si/Ge interface is abrupt. The results imply that thermally cracked GeH_4 is also promising for Ge ALE.With the SALE and thermal cracking ALE using hydride molecules proposed by the head investigator, atomically controlled epitaxy technologies for IV-group semiconductors are expected to be widely promoted and the methods will give a great contribution to the progress of Si/Ge quantum well devices. Less