Top Hat HELLISH (Hot electron light emitting and lasing in heterostructures)

Hot electron light emitting and lasing in semiconductor heterostructures (HELLISH) is a longitudinal transport structure comprising of a GaAs Quantum Well within an Al_xGa_1_-_xAs pn junction. The light emission from the HELLISH device was previously believed to be merely due to hot electron effects. In the current work, we showed, however, that the device can be operated even at low applied electric fields where the hot electron effects are essentially negligible. Thus, a novel model for operation with the new concept of 'quasi-flatband condition' is introduced. In order to investigate new functionalities of the HELLISH devices, a new structure with longer p-channel, nicknamed Top Hat HELLISH (THH), is also fabricated and demonstrated. In terms of the energy band profile, the HELLISH device has a monotonic build-in potential barrier along the heterojunction. The operation is through tilting the bands and hence allowing carrier diffusion into the active region under the quasi-flatband condition. However, in contrast, the THH has a warped energy band profile along the heterojunction. Thus one end is forward biased and the other end is reverse biased, which is the result of shortening the length of the top n-channel of the HELLISH device. Unlike the standard HELLISH, the THH device can simultaneously emit and detect light. This feature makes it possible to construct a wavelength converter. Furthermore, by incorporating a vertical cavity semiconductor optical amplifier (VCSOA) structure, the THH can be operated as an amplifier in the reflection mode along with an additional gate for optical modulation in the absorption section. The novel THH-wavelength converter and THH-amplifier/modulator were demonstrated for the GaAs/AlGaAs structures. However an initial attempt has been made to design and operates the THH device at a communication wavelength of 1300 nm using dilute nitrides (GalnNAs/GaAs material). (author)Available from British Library Document Supply Centre- DSC:DXN064973 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo