THz devices based on 2D electron systems

Abstract

In two-dimensional electron systems with mobility on the order of 1,000 -10,000 cm 2 /Vs, the electron scattering time is about 1 ps. For the THz window of 0.3 -3 THz, the THz photon energy is in the neighborhood of 1 meV, substantially smaller than the optical phonon energy of solids where these 2D electron systems resides. These properties make the 2D electron systems interesting as a platform to realize THz devices. In this paper, I will review 3 approaches investigated in the past few years in my group toward THz devices. The first approach is the conventional high electron mobility transistor based on GaN toward THz amplifiers. The second approach is to employ the tunable intraband absorption in 2D electron systems to realize THz modulators, where I will use graphene as a model material system. The third approach is to exploit plasma wave in these 2D electron systems that can be coupled with a negative differential conductance element for THz amplifiers/sources/detectors.

Influence of collector doping setback in the quantum transport characteristics of GaN/AlN resonant tunneling diodes

“…12) Over the last few years, resonant tunneling within IIInitride semiconductors has undergone a renaissance, thanks to recent breakthroughs in epitaxial growth, heterostructure design, and device fabrication techniques. [13][14][15][16][17][18][19][20][21][22][23][24] Since the first demonstration of repeatable room temperature negative differential conductance (NDC) in GaN/AlN resonant tunneling diodes (RTDs), 14,15) there has been a steady improvement in the current densities delivered by these devices. 23,24) More importantly, the robustness of this quantum transport regime has been experimentally verified with the demonstration of the first resonant tunneling microwave oscillator.…”

“…24,25) These milestones highlight the exciting prospects of nitridebased resonant tunneling injection for the engineering of new functionalities within the family of III-nitride electronic and photonic devices. [26][27][28][29] In contrast to traditional non-polar semiconductors, IIInitride heterostructures exhibit strong built-in polarization fields which dominate their electronic, optical, and piezoelectric properties. Owing to their magnitude, they influence the distribution of free carriers, control the strength and direction of the internal electric fields, and determine the conduction-band profile of the resonant tunneling cavity.…”