Transient Photocurrent Behavior of Multiple Quantum Well GaAs/Al_xGa_(1-x)As Electrode

Authors

Liu Yao, Institute of Photographic Chemistry, Academy Sinica, Beijing 100101
Xurui Xiao, Institute of Photographic Chemistry, Academy Sinica, Beijing 100101
Yuan Lin, Institute of Photographic Chemistry, Academy Sinica, Beijing 100101
Yiping Zeng, Institute of Semiconductors, Academy Sinica, Beijing 100083
Dianzhao Sun, Institute of Semiconductors, Academy Sinica, Beijing 100083
Haiqun Zheng, Institute of Semiconductors, Academy Sinica, Beijing 100083

Corresponding Author

Xurui Xiao

Abstract

Transient photocurrents induced by short light pulses at lattice-matched multiplequantum well (MQW)GaAs/Al_0.3)Ga_0.7 As electrodes were studied in the 1 ×10^-2 mol·dm^-3 ferrocene([Fc⁰]/[Fc⁺]=9/1)-0.1 mol·dm^-3 tetrabutylammonium tetrafluoroborate acetonitrile solutionin order to examine the relaxation photoprocesses and to evaluate kinetic parameters of superlattice electrodes.

GaAs/Al_0.3Ca_0.7 As MQW electrode consisting of 10 periods with each of GaAs well (5.3 nm) and Al_0.3Ga_0.7. As barrier (10 nm) showed two pronounced and well-resolved peak structures located at 1.503 eV and 1.699 eV in the photocurrent spectrum, corresponding to the theoretical allowedexcitonic transitions (Δn=0) for heavy holes (H11,H22)in the quantum well respectively.

Transient photocurrent spectra were measured by a monochromatic light pulse with 7 μs pulsewidth and 9 nJ·cm^-2 of energy at λ=800 nm preduced by a pulsed xenon lamp via amonochromator, and analyzed by Pade boplace transform method. Photocurrent transients werecharacterized by a rapid decays following by a slow exponent at the electrode potential varying from -2.3 V to 0 V vs SCE, and exhibited typical I-V behaviours of n-type semiconductor. Dual exponential transient photocurrent decay were demonstrated by the two segments with different slope inthe relations of normalized logarithm of photocurrent response and decay time, representing twoprocesses-RC (fast) and surface recombination (slow). By fitting the transient decay to the dualexponent function of the form: I(t)=A₁exp(-t/τ₂)+A₂exp(-t/τ₂), where t is the decay time, A₁,A₂ and τ₁,τ₂ correspond to the amplitudes and time constants of the fast and slow decaysrespectively. The kinetic parameters such as the normalized steady state photocurrent (I_s/G₀) and surface state lifetime (T_s) were determined in frequency domain. Both of the I_s/G₀ defined as therelative ratio of photogenerated carrier transferred from the electrode to electrolyte and the T_s reflectedthe rate of the surface recombination increased with the positive shifts of electrode potential, due tofast separation of photogenerated electron-hole pairs and slow surface recombination resulted by thelarger band bending created at more positive potential. Comparison with GaAs electrode, significantly larger I_s/G₀ were obtained in the potential range of -2.3 V to 0 V vs SCE,and longer T_s at morenegative electrode potential for MQW electrode ,indicating that the longer lifetime of exciton presentedin the MQW electrode leads to less bulk and surface recombination and higher concentration ofphotogenerated carriers at the interface. The increase of light to electric conversion efficiencies is, therefore, reasonably available in the MOW electrode systems.

Keywords

Superlattice(quantum well), Multiple quantum well, Transient photocurrent

DOI Link

https://doi.org/10.61558/2993-074X.1258

Publication Date

1995-02-28

Online Available Date

1995-02-28

Revised Date

1994-09-24

Received Date

1994-09-06

Recommended Citation

Liu Yao, Xurui Xiao, Yuan Lin, Yiping Zeng, Dianzhao Sun, Haiqun Zheng. Transient Photocurrent Behavior of Multiple Quantum Well GaAs/Al_xGa_(1-x)As Electrode[J]. Journal of Electrochemistry, 1995 , 1(1): 21-24.
DOI: 10.61558/2993-074X.1258
Available at: https://jelectrochem.xmu.edu.cn/journal/vol1/iss1/3