Spin transport and accumulation in the persistent photoconductor Al0.3Ga0.7As

Abstract

Electrical spin transport and accumulation have been measured in highly Si doped Al 0.3 Ga 0.7 As utilizing a lateral spin transport device. Persistent photoconductivity allows for the tuning of the effective carrier density of the channel material in situ via photodoping. Hanle effect measurements are completed at various carrier densities and the measurements yield spin lifetimes on the order of nanoseconds, an order of magnitude smaller than in bulk GaAs. These measurements illustrate that this methodology can be used to obtain a detailed description of how spin lifetimes depend on carrier density in semiconductors across the metal-insulator transition.

Bias current dependence of the spin lifetime in insulating Al0.3Ga0.7As

“…Details of the Fe/AlGaAs heterostructure, device geometry, and fabrication procedure have been presented previously. 13 In this device, the Fe electrode that the spins accumulate under is 50 Â 10 lm 2 and 5 nm thick. 20 The spin accumulation measurements were completed using the Hanle effect in a 3T geometry (see Fig.…”

“…11 Local and nonlocal spin accumulation has recently been detected electrically in the persistent photoconductor [17][18][19] Al 0.3 Ga 0.7 As:Si at various carrier densities by tuning the effective carrier density of the material in one sample in situ using photoexcitation. 13 The present letter focuses on the investigations of the bias and temperature dependences of the spin lifetime in this material at a carrier density of n ¼ 5 Â 10 16 cm À3 , which is on the insulating side of the metalinsulator transition (MIT) (n c ¼ 9 Â 10 16 cm À3 , see Ref. 19), as well as on the source and drain asymmetry of the spin accumulation signals in a 3T Hanle effect geometry.…”

“…The value of the spin lifetime obtained in this 3T experiment can be compared to non-local 4T transport results published previously on the same device. 13 For this carrier density and a bias of 265 6 8 lA, the spin lifetime obtained from a 4T transport measurement is 1.78 6 0.33 ns using the same Lorentzian fitting procedure. If we compare that to the spin lifetime obtained using the 3T spin accumulation method at comparable bias (from Fig.…”

“…The transport and accumulation of spins has been detected electrically in several semiconductors to date (GaAs 1,2 , Si [3][4][5][6] , InGaAs 7,8 , Ge [9][10][11][12] , AlGaAs 13 ), and the bias and temperature dependences of the spin signals have been investigated in these materials.…”

“…Local and nonlocal spin accumulation has recently been detected electrically in the persistent photoconductor [17][18][19] Al 0.3 Ga 0.7 As:Si at various carrier densities by tuning the effective carrier density of the material in one sample in situ using photoexcitation 13 .…”