Band-engineered quasi-AlGaN/GaN high-electron-mobility-avalanche-transit-time (HEMATT) oscillator: electro-optical interaction study in sub-mm frequency domain

A laterally oriented high-electron-mobility-avalanche-transit-time (HEMATT) diode with a prototypal quasi-AlGaN barrier has been designed. The proposed HEMATT diode is the first of its kind in high-power THz ATT device group. The mentioned quasi-AlGaN barrier consists of superfine epilayers of AlN/GaN that may be considered as a sustained quasi-AlGaN material where band offset and polarization field result in periodic perturbation. For the first time, a two-terminal (2 T) high-electron mobility ATT device with two-dimensional electron gas (2DEG) transport region has been introduced. Such 2DEG results in the band offset between AlGaN and GaN. Moreover, due to the lateral orientation of the proposed device such 2DEG lies along the transport region. Field plates are attached with the cathode terminal to provide necessary electronic confinement. The combined effect of these successfully eliminates the need of third terminal/gate unlike high-electron-mobility-transistors (HEMTs). The electron mobility similar to(1600-2000) cm(2)/V-sec in such 2DEG transport region is twice as high as normal GaN 2DEG mobility similar to 800 cm(2)/V-sec. Effect of such high electron mobility in any two-terminal device has never been investigated by any research group. This is due to excellent quantum confinement that results from extreme localization provided by the quasi-AlGaN barrier. Optoelectronic performance of the proposed device has been analyzed using updated version of in-house Strain-corrected Mixed Quantum Tunneling Drift-Diffusion (Sc-MQTDD) model, verified by experimental observations. The model incorporates carrier generation-recombination, diffusion, lattice-phonon interaction, phonon-scattering, phonon bottle-necking, polarization effects in GaN/AlGaN superlattice. Till date, highest reported DC to RF conversion efficiency, 23% and 27% and RF power output, 980 x 10(9)W/m(2) and 1163 x 10(9)W/m(2) are obtained from this newly proposed single- and array-type ATT diodes. Further, the opto-electrical interaction study in the UV region and thermal stability issues are duly addressed. UV responsivity and quantum efficiency are 0.7A/W and 80%, respectively, for the 3 x 3 array.