Photogalvanic effects for interband absorption in AlGaN∕GaN superlattices

Abstract

The linear and circular photogalvanic effects (CPGEs), induced by ultraviolet (325nm) radiation, have been observed in the (0001)-oriented Al0.15Ga0.85N∕GaN superlattices. The CPGE current changes sign upon reversing the radiation helicity, and it is up to two orders of magnitude larger than that obtained by far-infrared radiation. This result suggests the existence of a sizeable Rashba spin splitting in AlGaN∕GaN superlattices. It also provides a possibility for the generation of spin orientation-induced current at room temperature.

Spin dynamics in semiconductors

“…Therefore, all the linear in k terms are of the Rashba-type, 12 which makes them indistinguishable in experiments. Indeed, experiments revealed that the spin-orbit coupling is dominated by the Rashba-type spin-orbit coupling, where no effect that signals spin-orbit coupling of the form of (k x σ x − k y σ y ) was observed [247,[256][257][258][259][260]. The measured Rashba parameter lies in the range of 0.6 to 8 × 10 −12 eV m various conditions [251][252][253][254][261][262][263][264][265][266][267][268].…”

All-optical generation and detection of subpicosecond ac spin-current pulses in GaAs

“…Previously, optical injections of spinpolarized charge currents have been demonstrated through quantum interference in bulk GaAs 16 and by spin photogalvanic effect in several structures including GaAs quantum wells ͑QWs͒, [17][18][19] InAs QWs, 20 Si/Ge QWs, 21 and AlGaN/ GaN superlattices. [22][23][24][25] These spin currents are generated optically, without applying any external electric fields. However, in each of these studies currents were detected not by optical techniques but by measuring steady-state voltage [16][17][18][19][20][21][22][23][24][25] caused only by the charge component of the currents.…”

“…[22][23][24][25] These spin currents are generated optically, without applying any external electric fields. However, in each of these studies currents were detected not by optical techniques but by measuring steady-state voltage [16][17][18][19][20][21][22][23][24][25] caused only by the charge component of the currents. Therefore, not only has the degree of spin polarization of these photogenerated currents not measured but, strictly speaking, even the existence of a spin component of these currents has not been experimentally demonstrated since spin polarized carriers do not necessarily carry a spin polarized current.…”

Experimental observation of isotropic in-plane spin splitting in GaN∕AlGaN two-dimensional electron gas

“…Since the CPGE current is directly associated with the intrinsic spin splitting in a 2DEG sample, the angular dependent measurements of CPGE current will provide a direct way to measure the isotropy of the in-plane spin splitting in k space. Although the CPGE combined with the linear photogalvanic effect was reported by interband excitation, 17 in-plane spin splitting in wurtzite-type heterostructures have so far remained elusive. In this letter, we demonstrate experimentally an isotropic in-plane spin splitting in GaN / AlGaN 2DEG by monitoring the photocurrent induced by CPGE.…”