Implanted Impurities in Wide Band Gap Semiconductors

Abstract

Wide band gap semiconductors, mainly GaN, have experienced much attention due to their application in photonic devices and high-power or high-temperature electronic devices. Especially the synthesis of InxGa1-xN alloys has been studied extensively because of their use in LEDs and laser diodes. Here, In is added during the growth process and devices are already very successful on a commercial scale. Indium in nitride ternary and quaternary alloys plays a special role; however, the mechanisms leading to more efficient light emission in In-containing nitrides are still under debate. Therefore, the behaviour of In in GaN and AlN, the nitride semiconductor with the largest bandgap is an important field of study. In is also an important impurity in another wide band gap semiconductor – the II-VI compound ZnO where it acts as an n-type dopant. In this context the perturbed angular correlation technique using implantation of the probe111In is a unique tool to study the immediate lattice environment of In in the wurtzite lattice of these wide band gap semiconductors. For the production of GaN and ZnO based electronic circuits one would normally apply the ion implantation technique, which is the most widely used method for selective area doping of semiconductors like Si and GaAs. However, this technique suffers from the fact that it invariably produces severe lattice damage in the implanted region, which in nitride semiconductors has been found to be very difficult to recover by annealing. The perturbed angular correlation technique is employed to monitor the damage recovery around implanted atoms and the properties of hitherto known impurity – defect complexes will be described and compared to proposed structure models.

Nanostructures and thin films of transparent conductive oxides studied by perturbed angular correlations

“…Simulations using a variety of lattice parameters attributed for bulk ZnO were done in order to compare with the experimental results obtained by M. E. Mercurio et al [22] (V zz = 1.58(2) ⇥ 10 21 V /m 2 corresponding to the frequency ! 0 = 29.9(1) M rad/s) and by H. Wolf et al parameters of the samples used in these works were not reported and quite an amount of different lattice parameters for bulk ZnO can be found [5,9,20]. Simulations were then performed with the parameters reported by H. Sowa and H. Ahsbahs [20], a = 3.2489Å and c = 5.2053Å, resulting in a V zz = 1.428 ⇥ 10 21 V /m 2 .…”

“…The solubility of CdO in ZnO, besides being low, depends strongly on the growth conditions and technique that is used. Concerning PAC studies, ZnO bulk crystals have been studied using different probes [9] but, for technological purposes, thin films must be used. Thus, in this study, thin films of ZnO and Cd x Zn 1 x O (x = 0.16) were investigated.…”

Cd doping of AlN via ion implantation studied with perturbed angular correlation

“…In this work we present temperature dependent PAC measurements of 111m Cd and 117 Cd implanted into AlN. The obtained results are compared to previous 111 In measurements, that showed a complex of 111 In and a nitrogen-vacancy that forms during the annealing of the samples and is stable up to high temperatures [4]. Furthermore, it can be shown, that this complex is not formed with Cd when measured at room temperature [5], which indicates that Cd traps no defects.…”

“…4, although a second probe environment with a much larger EFG is observed [4]. Due to the fact, that the PAC-state is the same in both probes, this is an additional evidence, that Cd is incorporated on substitutional Al-sites which is known for In.…”

Ion implantation of Cd and Ag into AlN and GaN

“…Recent PAC studies suggest that Indium in GaN and AlN tends to trap a nitrogen vacancy, which may strongly influence the properties of InGaN and AlInN alloys and may play a role in the above mentioned mechanisms of exciton localisation [4]. PAC measurements using the probes 117 Cd, 111m Cd and 181 Hf show that this probe-vacancy complex does not form at other heavy impurities and is a peculiarity of In in IIInitrides [5]. In these studies the radioactive probes were introduced by ion implantation.…”