Terahertz emission spectroscopy of GaN-based heterostructures

Abstract

This study investigates the band bending profile of gallium-nitride-based heterostructures with respect to the change in the direction of the induced current in the out-of-plane plane direction, which gives the phase of the terahertz emission peak and can be detected by laser THz emission microscopy. We use a wavelength-tunable laser THz emission spectroscope to observe the transport of charges within the band bending regions, excitation of nearby photocarriers, and carrier scattering. We observe flip-flop peak-to-peak THz emission waveforms for a GaN heterostructure field-effect transistor (FET) compared to a strong THz emission radiated from an Al0.3Ga0.7N/GaN high-electron-mobility-transistor (HEMT). The flip-flop THz emission indicates the emission from various interfaces inside the FET structure, and intense THz emission from the HEMT structure indicates band-edge excitation. Our results provide a valuable perspective for characterizing complex heterostructures that provide insight into possible defects, carrier mobilities, and band bending of multilayer interface electronic devices.

How to use terahertz emission spectroscopy for wide bandgap semiconductor evaluation

“…We have applied TES and LTEM to Si-based materials and devices and proven that one can estimate various parameters, such as surface potential, work function, impurity doping density, defects density in passivation layers, surface state density, and so on, semi-quantitatively and non-contactly by just observing the THz radiation [8][9][10][11][12][13][14][15][16][17]. In the present work, we review the TES and LTEM application to wide bandgap semiconductors [18][19][20][21][22][23][24].…”