| AVS 57th International Symposium & Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM-TuA |
| Session: | Defects in Semiconductors and Oxides |
| Presenter: | I.A. Buyanova, Linköping University, Sweden |
| Authors: | I.A. Buyanova, Linköping University, Sweden M. Chen, Linköping University, Sweden |
| Correspondent: | Click to Email |
Dilute nitride alloys have in past years sparked a considerable interest because of their unusual physical properties and their potential device applications in visible light emitting diodes (LEDs), long wavelength telecommunications lasers on a GaAs substrate and highly efficient hybrid solar cells. Up to now, however, a major obstacle for full exploration of these devices is degradation of the radiative efficiency and carrier mobility of dilute nitrides when N content increases, mainly due to severe non-radiative (NR) recombination and carrier scattering. Many theoretical and experimental efforts were devoted to identifying the NRR centers, however, their origin is still being debated.
In this talk we will review our recent experimental results that have positively identified Ga interstitial defects as the dominant NR defects in Ga(In)NP and Ga(In)NAs epilayers and quantum wells by optical and spin resonance spectroscopy. Their formation is shown to strongly depend on growth methods (MBE or MOCVD) and conditions (growth temperature, bombardment by N ions, N flow, etc) as well as post-growth rapid thermal annealing and hydrogenation. In Ga(In)NAs, the carrier recombination process via these defects is shown to be strongly spin-dependent, which opens a door for spin manipulation of the process [1]. We demonstrate that strong spin-blockade of NR carrier recombination via these Ga interstitial defects can be achieved once the defect electrons are spin polarized. This results in a significant enhancement of light emission efficiency by up to 8 times, accompanied by a sizable increase in the non-equilibrium carrier lifetime. The defects formation is concluded to become thermodynamically favorable under the presence of N, possibly because of local strain compensation and seems to be unavoidable at least with the current technology. Therefore, demonstrated spin blockade of the associated carrier recombination appears to offer an attractive approach to strongly suppress NR shunt path.
Besides the Ga interstitial defects, we will show that severe nitrogen ion bombardment under non-equilibrium growth conditions during solid-source MBE could also trigger formation of an interfacial defect at a GaNP/GaP interface. The defect is identified to involve a PGa antisite or a Pi interstitial with a neighboring partner aligned along a <111> direction . The defect could be important in restricting carrier mobility in the related transistor structures and in reducing radiative efficiency of the GaNP-based LEDs.
[1] X.J. Wang, I.A. Buyanova, F. Zhao, D. Lagarde, A. Balocchi, X. Marie, C.W. Tu, J.C. Harmand and W.M. Chen, Nature Materials, 8, 198 (2009).