Nanoscale Impact Ionization and Electroluminescence in a Biased Scanning-Tunneling-Microscope Junction
Lehua Gu1, Shuang Wu1, Shuai Zhang1, and Shiwei Wu1,2,3,4*
1State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (MOE), and Department of Physics, Fudan University, Shanghai 200433, China 2Shanghai Qi Zhi Institute, Shanghai 200232, China 3Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, China 4Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
Abstract：Electroluminescence from a p-type GaAs(110) surface was induced by tunneling electrons in a scanning tunneling microscope under both polarities of bias voltage. The optical spectra exhibit a polarity-independent luminescence peak at 1.47 eV resulting from the exciton recombination. However, the quantum yield of photon emission at negative bias voltage is two orders of magnitude weaker than that at positive bias voltage. Moreover, the luminescence at negative bias voltage shows the linear dependence of bias voltage, distinct from the rapid rise due to resonant electron injection at positive bias. Furthermore, the threshold bias voltage for electroluminescence at negative bias is nearly twice the bandgap of GaAs, not simply satisfying the energy conservation for the creation of an electron–hole pair. Through theoretical calculation, we propose an impact ionization model to nicely explain the newly observed electroluminescence at negative bias voltage. We believe that this mechanism of impact ionization could be readily applied to other nanoscale optoelectronics including 2D semiconductors and 1D nanostructures.
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2022, Vol. 39 
