Effect of barrier width between GaAs/InGaAs/GaAs double coupled quantum wells on bipolar transport and terahertz radiation by hot carriers in lateral electric field

Abstract

The dependences of the current and integral intraband terahertz electroluminescence intensity on the electric field in the n-InGaAs/GaAs heterostructures with asymmetric double tunnel-coupled quantum wells under the conditions of bipolar lateral transport are established to differ qualitatively for different interwell barrier widths. In the case of the thick (∼50 Å) barriers at electric fields less than those corresponding to the Gunn instability, high-frequency current oscillations are observed, and the emission intensity monotonously increases with increasing electric field strength over the entire studied range up to 3 kV/cm. At small barrier widths (∼30 Å), the current oscillations are practically absent, and the emission intensity substantially increases with the field strength between 1.5 and 2 kV/cm. The emission intensity increase is explained by the addition of direct electron and hole transitions between the size-quantization subbands to the indirect intrasubband transitions. The observed differences may be explained by the different relationships between the interband radiative recombination time of the minority charge carriers (holes) in the narrow wells and the hole tunneling time into the wide wells, dependent on the interwell barrier width.