Electrical and High-Frequency Properties of Compensated GaN under Electron Streaming Conditions

Abstract

Conditions required for the streaming effect and the optical-phonon transit-time resonance to take place in a compensated bulk GaN are analyzed in detail. Monte Carlo calculations of the high-frequency differential electron mobility are carried out. It is shown that the negative dynamic differential mobility can be realized in the terahertz frequency range, at low lattice temperatures of 30-77 K, and applied electric fields of 3-10 kV/cm. New manifestations of the streaming effect are revealed, namely, the anisotropy of the dynamic differential mobility and a specific behavior of the diffusion coefficient in the direction perpendicular to the applied electric field. The theory of terahertz radiation transmission through the structure with an epitaxial GaN layer is developed. Conditions for the amplification of electromagnetic waves in the frequency range of 0.5-2 THz are obtained. The polarization dependence of the radiation transmission coefficient through the structure in electric fields above 1 kV/cm is found.

Peculiarities of THz-electromagnetic wave transmission through the GaN films under conditions of cyclotron and optical phonon transit-time resonances

“…Analyzing the peculiarities of THz-light transmission, the spectra of dynamic mobility will be used from ref. [13]. The spectra of , coefficients appear to be more significant at a higher electron concentration.…”

“…We apply the theory developed in the section 2 to the film of compensated GaN of cubic modification with the following parameters: concentration of ionized impurity [13], and it was shown that at these parameters OPTTR is most pronounced within the range of the applied electric fields 2 to 8 kV/cm. The low-field mobility  was found to reach the values around 5000 cm 2 /(Vs) (corresponding scattering time ps 57 .…”

Diffusion properties of electrons in GaN crystals subjected to electric and magnetic fields

“…For calculations of electron transport characteristics we used the single-particle algorithm of the Monte Carlo procedure [20,22,23,38]. Three main scattering mechanisms were taken into account: electron scatterings by ionized impurities, acoustic phonons and polar optical phonons.…”

“…In contrast to conventional A III B V materials, such as GaAs, InSb or InP, the widebandgap nitrides (for GaN the bandgap is 3.2 eV) are described by the large separation between the lower Г-valley and upper valleys separation (~1.2…1.5 eV for GaN), the high optical phonon energy, ћω0 (for GaN, ћω0 ≈ 92 meV), the strong electron-optical-phonon coupling (the Fröhlich constant is ~0.4 for GaN) and the high low-field mobility (at room to liquid nitrogen temperatures the mobility is ~1500…5000 cm 2 /V•s for GaN, [15]). These material properties of the nitrides are favorable for the realization of a specific streaming-like electron transport regime, which is characterized by a quasi-periodic electron motion in the momentum space [16][17][18][19][20] due to the threshold character of the electron-optical phonon emission. The streaming transport regime is possible at low lattice temperatures, T0, (kBT0 < ћω0, where kB is the Boltzmann constant) and small electron concentrations, Ne.…”

Elecron transport in crossed electric and magnetic fields under the condition of the electron streaming in GaN

“…Recently, we investigated conditions of streaming and OPTTR effects in the case of compensated GaN, where an undesirable influence of the non-elastic e e  scattering [10] can be avoided. We specified intervals of applied electric fields E (3…10 kV/cm), ambient temperatures T (30…150 K) and frequency ranges (0.2…2 THz), where streaming and OPTTR effects can occur [13,14]. Also, we investigated high-frequency properties of the compensated GaN under streaming conditions in the case of applied parallel magnetic field ( E H || ) [15,16] and found that this field has no effect on steady-state characteristics but essentially changes the frequency spectra of dynamic mobility tensor.…”