Valley current characterization of high current density resonant tunnelling diodes for terahertz-wave applications

Abstract

We report valley current characterisation of high current density InGaAs/AlAs/InP resonant tunnelling diodes (RTDs) grown by metal-organic vapour phase epitaxy (MOVPE) for THz emission, with a view to investigate the origin of the valley current and optimize device performance. By applying a dual-pass fabrication technique, we are able to measure the RTD I-V characteristic for different perimeter/area ratios, which uniquely allows us to investigate the contribution of leakage current to the valley current and its effect on the PVCR from a single device. Temperature dependent (20 – 300 K) characteristics for a device are critically analysed and the effect of temperature on the maximum extractable power (PMAX) and the negative differential conductance (NDC) of the device is investigated. By performing theoretical modelling, we are able to explore the effect of typical variations in structural composition during the growth process on the tunnelling properties of the device, and hence the device performance.

Micro-PL analysis of high current density resonant tunneling diodes for THz applications

“…Details about the fabrication process are reported elsewhere [18]. Measurements were conducted in the third quadrant to minimize self-heating and prevent catastrophic failure [7]. The peak and valley voltages and currents are indicated.…”

“…As for all quantum-effect devices [6], the RTD performance is critically dependent on crystal purity and heterointerface perfection. We previously demonstrated how ~80% of the parasitic valley current is associated with non-thermal inelastic scattering [7], and as a consequence, the RTD output power is limited by crystal-related imperfections.RTDs are composed of a single double-barrier QW generally growth by molecular beam epitaxy (MBE) or metal-organic vapor-phase epitaxy (MOVPE), despite the outstanding precision offered by these technologies, wafer characterization remains a difficult process, leading to knowledge barriers in…”

“…As for all quantum-effect devices [6], the RTD performance is critically dependent on crystal purity and heterointerface perfection. We previously demonstrated how ~80% of the parasitic valley current is associated with non-thermal inelastic scattering [7], and as a consequence, the RTD output power is limited by crystal-related imperfections.…”

Epitaxial Designs for Maximizing Efficiency in Resonant Tunneling Diode Based Terahertz Emitters

“…The reduction in IRE seen with certain combinations of well width & depth is attributed to the drop of the resonant state below the injection energy level. Further improvement of this figure may be achieved by reducing the carrier scattering within the structure, either by improving epitaxial processes or designs (discussed in the following section), or by reducing the operating device temperature [57]. An alternative material system with greater conduction band energy offsets may also enhance this figure.…”

Fitting of photoluminescence spectra for structural characterisation of high current density resonant tunnelling diodes for THz applications

“…We previously demonstrated how the RTD valley current and the device performance are not only limited by thermal effects, but mainly by interface scattering [4], with only 28% of the valley current being thermally activated, leaving space for significant improvement of the crystal quality. To optimize the epitaxial process, we first demonstrated the use of PL as rapid non-destructive characterization process [5].…”