P-type Conduction in Bulk ZnSe by Nitrogen Ion-Implantation
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P-TYPE CONDUCTION IN BULK ZnSe BY NITROGEN ION-IMPLANTATION
M. K. JIN*, T. YASUDA*, K. SHAHZAD** and J. L. MERZ* * Department of Electrical and Computer Engineering, University of California, Santa Barbara, CA 93106 ** Philips Laboratories, North American Philips Corporation, 345 Scarborough Road, Briarcliff Manor, N.Y. 10510 ABSTRACT P-type conduction in bulk ZnSe has been achieved using lx 1016 cm-2 nitrogen (N) ionimplantation followed by a high temperature rapid thermal annealing. Room temperature Hall effect measurements of the sample show that the hole concentration is -lx10 17 cm-3 , and the mobility is -30 cm2 /V-s. Photoluminescence (PL) measurements were performed to study the optical behavior of the samples, and the results show that the ion implantation damage can be partially repaired by thermal annealing at 9000 C or higher. Thermal degradation and recovery of the ion-implantation damage were studied as a function of the annealing temperature. INTRODUCTION ZnSe is one of the most promising II-VI semiconductors for blue light-emitting diodes (LEDs) and laser diodes (LDs) due to its direct band gap of 2.7 eV at room temperature. However, the large band gap of ZnSe brings with it difficulties in controlling the conductivity of this material. It is well known that the production of p-type ZnSe is especially difficult due to the lack of suitably well-behaved dopant sources and doping methods. In recent years, modem growth techniques of molecular beam epitaxy (MBE) and metalorganic chemical vapor deposition (MOCVD) have shown the possibility of improving the conductivity of ZnSe. Several reports have been published claiming p-type ZnSe by in-situ doping [1-10]. However, it is still difficult to control p-type conductivity due to the lack of suitable dopant sources for these techniques. Ion-implantation techniques promise the advantage of control of specific impurities introduced into the crystal. Several years ago, a few groups reported p-type conversion in bulk ZnSe by ion-implantation of lithium, nitrogen and phosphorus [11-13]. However, the conductivity of these bulk ZnSe samples was too low for device applications. More recently, the fabrication of p-n junction using MBE grown ZnSe implanted with nitrogen has been reported [4]. We have confirmed that nitrogen behaves as a shallow acceptor [14] using a low dose (lx1013 cm-2) N+ implantation in MBE grown ZnSe followed by rapid thermal annealing (RTA) [15]. However, due to the high resistivity of these samples with this low dose implantation, it was not possible to make electrical measurements in our previous work. We observed from these experiments that the samples with a high dose ion-implantation require a high temperature annealing. However, high temperature annealing of epitaxial grown ZnSe causes a serious inter-diffusion of unwanted species at the interface of a heteroepitaxial layer [16]. Bulk ZnSe has no such inter-diffusion problems, which is a great advantage in performing high dose ion-implantation studies. This will be the topic of the presen
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