Wu Mingjian, Luna Esperanza, Puustinen Janne, Guina Mircea, Trampert Achim
Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin, Germany.
Nanotechnology. 2014 May 23;25(20):205605. doi: 10.1088/0957-4484/25/20/205605. Epub 2014 Apr 30.
We report the formation and phase transformation of Bi-containing clusters in GaAs(1-x)Bi(x) epilayers upon annealing. The GaAs(1-x)Bi(x) layers were grown by molecular beam epitaxy under low (220 °C) and high (315 °C) temperatures and subsequently annealed using different temperatures and annealing times. Bi-containing clusters were identified only in the annealed samples that were grown at low temperature, revealing a relatively homogeneous size distribution. Depending on the annealing temperature and duration, the clusters show different sizes ranging from 5 to 20 nm, as well as different crystallographic phase, being coherently strained zincblende GaAs(1-x)Bi(x) (zb Bi-rich Ga(As, Bi)) clusters or rhombohedral pure Bi (rh-Bi) clusters. We found that: (1) the formation of the zb Bi-rich Ga(As, Bi) clusters is driven by the intrinsic tendency of the alloy to phase separately and is mediated by the native point defects present in the low temperature grown epilayers; (2) the phase transformation from zb Bi-rich Ga(As, Bi) to rh-Bi nucleates in zincblende {111} planes and grows until total consumption of Bi in the GaAs matrix. We propose a model accounting for the formation and phase transformation of Bi-containing clusters in this system. Furthermore, our study reveals the possibility to realize self-organized zb Bi-rich Ga(As, Bi) clusters that can exhibit QD-like features.
我们报道了在退火过程中，GaAs(1-x)Bi(x)外延层中含铋团簇的形成和相变。通过分子束外延在低温（220°C）和高温（315°C）下生长GaAs(1-x)Bi(x)层，随后使用不同温度和退火时间进行退火。仅在低温生长的退火样品中鉴定出含铋团簇，其尺寸分布相对均匀。根据退火温度和持续时间，团簇呈现出5至20纳米范围内的不同尺寸，以及不同的晶体相，即相干应变闪锌矿GaAs(1-x)Bi(x)（zb富铋Ga(As, Bi)）团簇或菱面体纯铋（rh-Bi）团簇。我们发现：（1）zb富铋Ga(As, Bi)团簇的形成是由合金相分离的内在趋势驱动的，并由低温生长外延层中存在的本征点缺陷介导；（2）从zb富铋Ga(As, Bi)到rh-Bi的相变在闪锌矿{111}平面上形核，并生长直至GaAs基体中的铋完全消耗。我们提出了一个解释该系统中含铋团簇形成和相变的模型。此外，我们的研究揭示了实现具有类量子点特性的自组织zb富铋Ga(As, Bi)团簇的可能性。
