Room-Temperature Defect-Enabled Spin Functionality in GaAs-Based Coumpound Semiconductors

Semiconductor spintronics is a newly emerging research field that explores the spin degree of freedom, in addition to charge of the electron, for future electronics, photonics and quantum information technology. The success of spintronics relies on our ability to create, maintain, manipulate and detect spin orientation and coherence at room temperature (RT). During recent years, we have witnessed impressive progresses in developments of novel concepts and innovative approaches in these areas. Unfortunately, a vast majority of earlier achievements have been restricted to cryogenic temperatures and with a rather low efficiency, often requiring an external magnetic field. Here, we present our recent work on a new and unconventional approach of RT defect-enabled spin functionality in a non-magnetic semiconductor without requiring a magnetic layer or external magnetic fields. We demonstrated efficient spin filtering in Ga(In)NAs thin films and nanostructures, enabled by Ga self-interstitials, which is capable of generating a remarkably high spin polarization degree (> 40%) of conduction electrons at RT [1]. We also provided the first experimental demonstration of an efficient RT spin amplifier based on defect engineered Ga(In)NAs with a spin gain up to 2700%! [2] Such a spin amplifier is shown to be capable of amplifying a fast-modulating input spin signal while truthfully maintaining its time variation of the spin-encoded information. By taking advantage of the spin amplification effect, we showed that Ga(In)NAs quantum structures can be employed as efficient RT optical spin detectors, with spin detection efficiency well exceeding 100%. Combining the spin-filtering effect and hyperfine coupling, we further achieved the first realization of RT nuclear spin hyperpolarization in semiconductors via conduction electrons [3], relevant to practical applications of future solid-state quantum computation using nuclear spin qubits and in highly sensitive magnetic resonance imaging. We also demonstrated the potential of such spin engineering to significantly improve performance of spin light-emitting devices and efficiency of photovoltaic devices. Such approaches could potentially provide an attractive, alternative solution to the current and important issues on RT spin-functional semiconductors for future spintronics and spin-photonics.

[1] X.J. Wang et al. Nature Materials 8, 198 (2009)

[2] Y. Puttisong et al. Adv. Materials 25, 738 (2013).

[3] Y. Puttisong et al., Nature Communications. 4, 1751 (2013).