Electroluminescence from GaAs/AlGaAs Heterostructures in Strong in-Plane Electric Fields: Evidence for k- and Real-Space Charge Transfer
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- 作者：Weilu Gao ; Xuan Wang ; Rui Chen ; David B. Eason ; Gottfried Strasser ; Jonathan P. Bird ; Junichiro Kono
- 刊名：ACS Photonics
- 出版年：2015
- 出版时间：August 19, 2015
- 年：2015
- 卷：2
- 期：8
- 页码：1155-1159
- 全文大小：457K
- ISSN：2330-4022
文摘
In the Gunn effect, which occurs in certain semiconductors in strong electric fields, electrons are driven out of a low-mass central valley into a heavy-mass side valley in k (momentum) space, ultimately resulting in negative differential resistance (NDR). Recently, there has been interest in the possibility of exploiting this phenomenon in heterostructured semiconductors, as a means to realize novel terahertz sources. Here, we demonstrate that a GaAs/AlGaAs heterostructure planar Gunn diode exhibits both NDR and electroluminescence (EL), the characteristics of which are consistent with the combined action of simultaneous k-space and real-space electron transfer. By making simultaneous electrical-transport and EL measurements, we reveal the following scenario as a function of the applied voltage. At sufficiently large bias, the onset of k-space transfer gives rise to NDR and results in the formation of traveling high-field domains. As each domain travels toward the anode, impact ionization taking place within it results in electron鈥揾ole pair generation and concomitant recombination. While some of this recombination takes place within the GaAs, it also occurs within the AlGaAs barrier after electrons undergo real-space tunneling into this layer from the GaAs. The real-space transfer is identified through the presence of a broad spectral peak in the EL consistent with the AlGaAs gap. Both the GaAs and AlGaAs EL peaks increase in intensity superlinearly with increasing bias, reflecting the nonlinear current鈥搗oltage characteristic of the device. Furthermore, we map out the spatial distribution of EL intensity in a long-channel device and observe the strongest EL near the anode, consistent with the notion that the high-field domain grows as it propagates from the cathode toward the anode. This planar Gunn diode provides a good platform for high-electric-field effect investigations in semiconductors under low bias and possible applications for terahertz technology.