报告人：周生强 博士 （德国德雷斯顿－罗森道夫海姆霍兹研究中心，Helmholtz-Zentrum Dresden-Rossendorf，Dresden，Germany）
邀请人：徐庆宇
时间：2013年10月08号上午10点
地点：田家炳楼南203
PPT：英文
报告语言：中文
周生强博士的简历：
1999年，北京大学技术物理系毕业，学士学位
2002年，北京大学技术物理系毕业，硕士学位
2007年，德国德雷斯顿理工大学物理系，博士学位
2007年-2010年，德国德雷斯顿－罗森道夫海姆霍兹研究中心，博士后
2010年-2011年，北京大学特聘研究员
2011年-现在，德国德雷斯顿－罗森道夫海姆霍兹研究中心，海姆霍兹杰出青年科学家研究小组组长
报告摘要：
Doping semiconductors is an essential issue for device fabrication. Ion implantation followed by annealing is a well-established method to dope Si and Ge. This approach has been maturely integrated with the IC industry production line. The solubility limit is a fundamental barrier for dopants incorporated into a specific semiconductor. Nowadays, the demands for functional materials require a supersaturated doping of semiconductors, i.e., the dopant concentration should be in the percent range. For instance for spintronic applications one needs to prepare magnetic semiconductors which are doped with up to 5-10% Mn [1]. For multiband solar cells one needs to dope semiconductors with deep levels at a concentration large enough to form impurity bands in the bandgap of the semiconductor host material. The impurity bands lead to an increased absorption of the IR solar spectrum. The efficiency can be as high as 60% [2]. The above-mentioned two types of functional materials are attracting huge research interests due to their potential use in devices with new functionalities.
To fabricate the above-mentioned materials, we have to overcome the low solid solubility limit of transition metals or deep-level dopants in semiconductors, i.e. to hyper-dope semiconductors. However, the goal is not only to introduce a large number of dopant atoms, but also to ensure that these atoms are electrically active. However, at high concentrations, dopant atoms usually tend to cluster. Therefore, one needs highly nonequilibrium methods to introduce enough dopants and a short-time annealing to activate them. Both ion implantation and pulsed-laser (or flash-lamp) annealing occur far enough from thermodynamic equilibrium conditions. Ion implantation introduces enough dopants. The subsequent short-time annealing deposits energy in the near-surface region to drive a rapid liquid-phase epitaxial growth. Such a nonequilibrium process maintains the supersaturation induced by ion implantation.
In this talk, I will make anoverview of the activities in my group utilizing ion implantation and short time annealing. These activities includesynthesizing full spectrum of III-V:Mn diluted magnetic semiconductors [3-5], optical property modification of GaAs [6-7] and metal-insulator transition in Se/S doped Si.
Reference
1. T. Dietl, H. Ohno, F. Matsukura, J. Cibert, and D. Ferrand, Science 287, 1019 (2000).
2. A.Luque and A.Martí, Phys. Rev. Lett. 78, 5014 (1997).
3. D. Bürger, S. Zhou, et al., Application of pulsed laser annealing to ferromagnetic GaMnAs, Phys. Rev. B 81, 115202 (2010).
4. S. Zhou, et al., The importance of hole concentration in establishing carrier-mediated ferromagnetism in Mn doped Ge, Appl. Phys. Lett. 96, 202105 (2010).
5. S. Zhou, et al. Ferromagnetic InMnAs on InAs Prepared by Ion Implantation and Pulsed Laser Annealing, Appl. Phys. Express 5, 093007 (2012)
6. S. Prucnal, …, S. Zhou, Temperature stable 1.3 μm emission from GaAs, Optics Express, 20, 26075-26081 (2012).
7. K. Gao, …, S. Zhou, Origin and enhancementof the 1.3 μm luminescence from GaAs treated by ion-implantation and flash lamp annealing, J. Appl. Phys. 114, 093511 (2013).