Identification of Defect Levels in III-V Semiconductors Using Radioactive Isotopes

半导体物理学中使用的光谱学技术，如光致发光（PL）和霍尔效应，能够检测和表征带隙状态，但不能揭示其微观起源的信息。为了克服电学和光学方法的这种化学“盲目性”，目前的方法是使用放射性同位素作为示踪剂。由于特征浓度根据核衰变规律发生变化，它们参与了电子带隙态的形成，这是可以肯定的，也可以否定的。以定量控制的方式掺杂多种放射性同位素的半导体，只有通过离子注入才能实现。氮化镓及其含氮化镓和氮化镓的合金由于具有光电器件的潜力，在实际半导体研究中是最有趣的一类材料之一。与其他III-V化合物相比，在这些体系中植入掺杂剂的电激活更为复杂，因为这种材料既具有需要高退火温度的强原子间键，又具有高蒸汽压的成分N。因此，这些植入研究的必要前提是使用这些掺杂剂的放射性同位素明确识别与GaN中潜在掺杂原子相关的PL信号和电学性质。在许多AB型化合物半导体（如GaAs）中，一类重要的内在缺陷是A原子位于B位（AB）或相反位置的反位。GaAs中GaAs反位体的电子能级是多少仍然是一个悬而未决的问题。在GaAs中以可控的方式产生GaAs反位缺陷并避免在生产过程中引入任何其他缺陷的独特方法是将放射性71As嬗变为稳定的71Ga。这种嬗变可以被PL跟踪，并且可能在带隙中由于对位而产生的状态可以被清楚地识别出来。

Spectroscopic techniques used in semiconductor physics like photoluminescence (PL) and Hall-effect that are able to detect and to characterize band gap states do not reveal information about their microscopic origin. To overcome this chemical "blindness" of the electrical and optical methods the present approach is to use radioactive isotopes as a tracer. Because of the characteristic concentration change according to the nuclear decay law, their involvement in the formation of electronic band gap states can be confirmed or denied definitely. Doping semiconductors with a variety of radioactive isotopes isotopically clean in a quantitatively controlled way is only realizable by ion implantation. GaN and its alloys with AlN and InN are one of the most interesting classes of materials in actual semiconductor research due to their potential as optoelectronic devices. The electrical activation of implanted dopants into these systems is more complex compared to other III-V compounds since this materials have both strong inter-atomic bonding demanding high annealing temperatures, and a constituent, N, having a high vapor pressure. An imperative prerequisite for these implantation studies is therefore the unambiguous identification of the PL signals and electrical properties related to potential doping atoms in GaN using radioactive isotopes of these dopants. An important class of intrinsic defects in many compound semiconductor of type AB like GaAs are antisites where an A atom is placed on a B site (AB) or vice versa. It is still an open question what the electronic levels of the GaAs antisite in GaAs are. A unique way to create GaAs antisite defects in GaAs in a controlled way and to avoid the introduction of any other defects during the production process is the transmutation of radioactive 71As to stable 71Ga. This transmutation can be followed up by PL and possibly created states in the band gap due to antisites can be clearly identified.