High-field electron transport in doped ZnO

Current-voltage characteristics have been measured for ZnO:Ga and Zn:Sb epitaxial layers with electron densities ranging from 1.4x10(17) cm(-3) to 1.1 x 10(20) cm(-3). Two-terminal samples with coplanar electrodes demonstrate virtually ohmic behavior until thermal effects come into play. Soft damage of the samples takes place at high currents. The threshold power (per electron) for the damage is nearly inversely proportional to the electron density over a wide range of electron densities. Pulsed voltage is applied in order to minimize the thermal effects, and thus an average electric field of 150 kV cm(-1) is reached in some samples subjected to 2 ns voltage pulses. The results are treated in terms of electron drift velocity estimated from the data on current and electron density under the assumption of uniform electric field. The highest velocity of similar to 1.5 x 10(7) cm s(-1) is found at an electric field of similar to 100 kV cm(-1) for the sample with an electron density of 1.4 x 10(17) cm(-3). The nonohmic behavior due to hot-electron effects is weak, and the dependence of the electron drift velocity on the doping resembles the variation of mobility

Electron drift velocity in lattice-matched AlInN/AlN/GaN channel at high electric fields

Hot-electron transport was probed by nanosecond-pulsed measurements for a nominally undoped two-dimensional channel confined in a nearly lattice-matched Al0.82In0.18N/AlN/GaN structure at room temperature. The electric field was applied parallel to the interface, the pulsed technique enabled minimization of Joule heating. No current saturation was reached at fields up to 180 kV/cm. The effect of the channel length on the current is considered. The electron drift velocity is deduced under the assumption of uniform electric field and field-independent electron density. The highest estimated drift velocity reaches ∼3.2×107 cm/s when the AlN spacer thickness is 1 nm. At high fields, a weak (if any) dependence of the drift velocity on the spacer thickness is found in the range from 1 to 2 nm. The measured drift velocity is low for heterostructures with thinner spacers (0.3 nm)

High-Frequency Noise Sources in Quantum Wells

Hot-electron noise is investigated for InGaAs and InAs quantum wells containing a two-dimensional electron gas channel in a pulsed electric field applied parallel to the interfaces. Noise sources resulting from hot-electron "thermal" motion, electron temperature fluctuations, and real-space transfer are observed. The experimental results on hot-electron "thermal" noise are used to estimate energy relaxation time in the field range where other sources do not play any important role. Measurements of noise anisotropy in the plane of electron confinement are used to discuss real-space-transfer noise. High-frequency noise technique is used to study hot-electron trapping, and trap location in InAlAs/InGaAs/InAlAs heterostructure channels is determined

Hot-Phonon Decided Carrier Velocity in AlInN/GaN Based Two-Dimensional Channels

Nanosecond-pulsed measurements of hot-electron transport were performed for a nominally undoped two-dimensional channel confined in a slightly strained $Al_{0.8}In_{0.2}N$/AlN/GaN and nearly lattice matched $Al_{0.84}In_{0.16}N$/AlN/GaN heterostructures at room temperature. No current saturation is reached because we minimized the effect of the Joule heating. The electron drift velocity is deduced under assumption of uniform electric field and field-independent electron density. The estimated drift velocity ≈ 1.5 × $10^7$ cm/s at 140 kV/cm bodes well with the value of hot-phonon lifetime exceeding 0.1 ps

The Electric Field and Temperature Dependence of Conductance of Two-Dimensional Electron Gas in AlGaN/AlN/GaN

The two-dimensional gas in AlGaN/AlN/GaN heterostucture with a very thin (0.6 nm) AlN spacer was investigated by conductivity relaxation measurements in 86-300 K temperature range. The results show the presence of two exponential relaxation processes characterized by different characteristic time constants. Parameters of the fast and slow components of the processes differently depend on the electric field and temperature. The fast process is attributed to influence of the electric field on the barrier formed by the spacer, while the slow process is attributed to the hot-electron capture out of the channel followed by electron thermal release

High-Frequency Noise Sources in Quantum Wells

Hot-electron noise is investigated for InGaAs and InAs quantum wells containing a two-dimensional electron gas channel in a pulsed electric field applied parallel to the interfaces. Noise sources resulting from hot-electron "thermal" motion, electron temperature fluctuations, and real-space transfer are observed. The experimental results on hot-electron "thermal" noise are used to estimate energy relaxation time in the field range where other sources do not play any important role. Measurements of noise anisotropy in the plane of electron confinement are used to discuss real-space-transfer noise. High-frequency noise technique is used to study hot-electron trapping, and trap location in InAlAs/InGaAs/InAlAs heterostructure channels is determined

Measurements of volt-ampere characteristics of wide gap semiconductor devices in nanosecond time scale

Measurements of volt-ampere characteristics of a nitride and carbide wide gap semiconductor devices using power electrical pulses of nanosecond duration eliminate Joule heating of the devices. However the devices operating at high electric field and having structures of nanometer size may be damaged by short electrical pulses due to consequence of overheating which begins at submicron inhomogeneities during the pulse rise time