THz Hot-Electron Micro-Bolometer Based on Low-Mobility 2-DEG in GaN Heterostructure

We present the results on design, fabrication, and characterization of a hot-electron bolometer based on low-mobility 2-D electron gas (2-DEG) in an AlGaN/GaN heterostructure. The characterization of our hot-electron bolometers demonstrates that the following can be achieved simultaneously: 1) strong coupling to incident THz radiation due to strong Drude absorption; 2) significant THz heating of 2-DEG due to the small value of the electron heat capacity; and 3) high responsivity due to the strong temperature dependence of 2-DEG resistance. Low contact resistance achieved in our devices ensures that THz radiation couples primarily to the 2-DEG. Due to a small electron momentum relaxation time, the real part of the 2-DEG sensor impedance is ~50-100 Ω, which provides good impedance matching between sensors and antennas. The room temperature responsivity of our devices reaches ~0.04 A/W at 2.55 THz along with a noise equivalent power of ~5 nW/Hz^1/2.