| AVS 57th International Symposium & Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM-TuA |
| Session: | Defects in Semiconductors and Oxides |
| Presenter: | Y. Jin, University of Michigan |
| Authors: | Y. Jin, University of Michigan R.M. Jock, University of Michigan H. Cheng, University of Michigan C. Kurdak, University of Michigan R.S. Goldman, University of Michigan |
| Correspondent: | Click to Email |
(In)GaAsN alloys with a few percent nitrogen have potential applications in long wavelength optoelectronic devices, such as infrared laser diodes, heterojunction bipolar transistors, and high efficiency solar cells. However, due to the large size and electronegativity differences between As and N, the formation of several point defect complexes has been predicted, likely leads to the limited optical emission efficiency and minority carrier transport properties in (In)GaAsN alloys. In this work, we investigate the influence of two types of N-related point defect complexes, Si-N complexes and N interstitials, on the electronic and optical properties of InGaAsN alloys.
The presence of Si-N defect complexes is first suggested by a decrease in carrier concentration, n, with increasing N-composition observed in GaAsN:Si films but not in modulation-doped heterostructures. In addition, for GaAsN:Te (GaAsN:Si), n increases substantially (minimally) with annealing-T, suggesting a competition between annealing-induced Si-N complex formation and a reduced concentration of N-related traps. Since Si-N complex formation is enhanced for GaAsN:Si growth with the (2 x 4) reconstruction, which has limited group V sites for As-N exchange, the (Si-N)As interstitial pair is identified as the dominant Si-N complex.
For the investigation of N interstitial defects, we compared the structural and electronic properties of GaAsN films before and after annealing. Nuclear reaction analysis (NRA) reveals an annealing-induced decrease in the interstitial N concentration, fint, while the total N composition remains constant. Corresponding signatures for the reduced fint are apparent in Raman spectra. For as-grown GaAsN films, low T transport measurements reveal two distinct T-dependent regimes of n: a T-independent regime > 150K, and a thermally-activated regime <150K. Meanwhile, persistent photoconductivity effect (PPC) was observed up to 160K, with the photo-capture barrier determined to be 350 - 400 meV. These two phenomena are reminiscent of the behavior of n-type AlGaAs due to the presence of DX-center levels, suggesting the presence of similar N-induced defect levels in GaAsN. After annealing, the thermal activation of n and the PPC effect are both suppressed, accompanied by the decrease in fint revealed by NRA, suggesting the association of these two phenomena with N interstitials.
This work is supported by NSF-FRG, grant # DMR-0606406, monitored by L. Hess