Investigation of molecular co-doping for low ionization energy p-type centers in (Ga,Al)N
- PDF / 207,558 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 106 Downloads / 135 Views
Y10.44.1
Investigation of molecular co-doping for low ionization energy p-type centers in (Ga,Al)N Zhe Chuan Feng, Adam M. Payne, David Nicol, Paul D. Helm and Ian Ferguson* Electrical & Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0250. * [email protected] Jayantha Senawiratne, Martin Strassburg and Nikolaus Dietz Department of Physics and Astronomy, Georgia State University, Atlanta, GA, 30303, USA. Axel Hoffmann and Christoph Hums Institute of Solid State Physics, Technical University of Berlin, 10623 Berlin, Germany. ABSTRACT This work initiates an investigation of molecular co-doping to produce p-type centers in (Ga,Al)N with ionization energies lower than Mg. Dopant complexes can be formed between a doubly ionized acceptor such as (Cu, Li or Ag) and a singly ionized donor (silicon). Ion implantation of Cu, Li and Ag into silicon doped GaN films grown by Metalorganic Chemical Vapor Deposition (MOCVD) has been performed. Secondary ion mass spectroscopy (SIMS) data confirmed the simulated depth profile. High resolution X-ray diffraction and Raman spectroscopy were used to characterize the crystalline damage and subsequent recovery upon anneal. A complete recovery was observed after high temperature (700-900°C) annealing. Low temperature (6K) photoluminescence (PL) for Cu-implanted GaN showed bands identified with crystalline lattice damage due to the Cu-implantation. The annealed samples showed recovery of standard crystalline GaN features. Additional donor-acceptor pair features are observed below 3.35 eV indicating the existence of an acceptor state. INTRODUCTION GaN (and its alloys with Indium and Aluminum) has become the dominant material system for the fabrication of light emitting diodes operating in the blue and ultra-violet ranges. One of the major obstacles to overcome for the development of electronics using GaN-based materials is the lack of a good p-type dopant. Once Nakamura1,2 showed that Mg could be used as an acceptor, GaN was rapidly developed into a commercial product—blue LEDs. However, Mg as a dopant is far from ideal. Mg is an acceptor in GaN residing between 180 meV to 250 meV from the valence band edge making ionization difficult at room temperature.3,4 This problem is greater at shorter wavelengths, and higher aluminum concentrations, due to a further deepening of this center. Thus Mg is only used because no other alternative exists. By solving this problem, it would be possible to make not just more efficient blue (and UV) LEDs, but it would also make possible improved high current injection devices, such as blue and UV lasers. The use of dopant complexes or molecular co-dopants, has been investigated towards the goal of improving p-type doping in GaN. Katayama-Yoshida and Yamamoto5,6 have suggested that co-doping of certain elements might create more shallow-lying acceptor states, based on theoretical models and simulations of co-doped materials. Their work implies that multiple codopants might preferentially form complexes which themselves lie closer to th
Data Loading...
