Coherent vertical electron transport and interface roughness effects in AlGaN/GaN intersubband devices

Abstract

We investigate electron transport in epitaxially grown nitride-based resonant tunneling diodes (RTDs) and superlattice sequential tunneling devices. A density-matrix model is developed, and shown to reproduce the experimentally measured features of the current-voltage curves, with its dephasing terms calculated from semi-classical scattering rates. Lifetime broadening effects are shown to have a significant influence in the experimental data. Additionally, it is shown that the interface roughness geometry has a large effect on current magnitude, peak-to-valley ratios and misalignment features; in some cases eliminating negative differential resistance entirely in RTDs. Sequential tunneling device characteristics are dominated by a parasitic current that is most likely to be caused by dislocations; however, excellent agreement between the simulated and experimentally measured tunneling current magnitude and alignment bias is demonstrated. This analysis of the effects of scattering lifetimes, contact doping and growth quality on electron transport highlights critical optimization parameters for the development of III-nitride unipolar electronic and optoelectronic devices. V C 2015 AIP Publishing LLC. [http://dx

New Tunneling Features in Polar III-Nitride Resonant Tunneling Diodes

“…Transfer matrix calculations by Sakr et al showed the connection between the strong polarization fields and the asymmetric I-V characteristics [44]. More recently, after repeatable III-nitride RTD behavior was achieved, the focus was mainly on the forward bias resonance [25][26][27]29]. It should be noted, however, that the internal polarization fields markedly manifest also in the reverse bias regime giving rise to a characteristic threshold voltage V th given by Eq.…”

“…More recently, III-nitride RTDs with low Al-composition AlGaN barriers have also been studied at cryogenic temperatures [25][26][27]. These devices, grown on freestanding GaN substrates (with low dislocation densities ∼5 × 10 6 cm −2 ), feature small mesa areas of ∼16 μm 2 aimed towards minimizing the number of defects per device.…”

Infinite-Period Density-Matrix Model for Terahertz-Frequency Quantum Cascade Lasers

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Design considerations for GaN/AlN based unipolar (opto-)electronic devices, and interface quality aspects

“…Resonant tunnelling diodes (RTDs) are interesting devices in their own right, and also the simplest devices in which vertical tunneling and scattering transport can be extensively investigated, both experimentally and theoretically: the experience might then be transferred to the design of more complicated, optoelectronic devices. With these aims we have investigated electron transport in epitaxially grown nitridebased resonant tunneling diodes (RTDs), as well as in superlattice-type sequential tunneling devices [3]. The density-matrix model was developed, and shown to be able to reproduce the experimentally measured current-voltage characteristics, with the dephasing terms in the model calculated from semi-classical scattering rates.…”