Quantum Confinement in High Electron Mobility Transistors

Abstract

Modulation-doped semiconductor nanostructures exhibit extraordinary electrical and optical properties that are quantum mechanical in nature. The heart of such structures lies in the heterojunction of two epitaxially grown semiconductors with different band gaps. Quantum confinement in this heterojunction is a phenomenon that leads to the quantization of the conduction and the valence band into discrete subbands. The spacing between these quantized bands is a very important parameter that has been perfected over the years into device applications. Most of these devices form lowdimensional charge carriers that potentially allow optical transitions between the subbands in such nanostructures. The transition energy differences between the quantized bands/levels typically lie in the infrared or the terahertz region of the electromagnetic spectrum and can be designed according to the application in demand. Thus, a proper understanding and a suitable external control of such intersubband transitions (ISTs) are not only important aspects of fundamental research but also a necessity for optoelectronic device applications specifically towards closing the terahertz gap.

A Novel Approach for Room-Temperature Intersubband Transition in GaN HEMT for Terahertz Applications

“…It is very difficult to distinguish the defects-or traps-assisted transitions, thermal transitions and ISBTs in the IV characteristics of FET. However, electrical tuning of ISBT in GaAs HEMT has been demonstrated [59]. There are three following key challenges involved in supporting the ambient ISBT mechanism in FET/HEMT.…”

“…It is very difficult to negligible thermal energy contribution. Thermal occupation of electrons in a higher subband may prevent the observation of ISBT at ambient temperature [59]. Measurement are done at ambient as well as low temperature in vacuum condition with a precise and accurate temperature controller to quantified the thermal transitions.…”

Calculation electrical conductivity a two-dimensional electron gas of AlGaN/GaN-based transistors with high electron mobility

“…The charge carrier motion is confined in the direction of the layer thickness. It is possible to configure interband transitions in heterostructures with the help of external fields [1]. The setting mechanism is related to the Stark effect and allows the use of modulators and detectors in the terahertz radiation range.…”