Measurements of temperature characteristics and estimation of terahertz negative differential conductance in resonant-tunneling-diode oscillators

Abstract

The temperature dependences of output power, oscillation frequency, and current-voltage curve are measured for resonant-tunneling-diode terahertz (THz) oscillators. The output power largely changes with temperature owing to the change in Ohmic loss. In contrast to the output power, the oscillation frequency and current-voltage curve are almost insensitive to temperature. The measured temperature dependence of output power is compared with the theoretical calculation including the negative differential conductance (NDC) as a fitting parameter assumed to be independent of temperature. Very good agreement was obtained between the measurement and calculation, and the NDC in the THz frequency region is estimated. The results show that the absolute values of NDC in the THz region significantly decrease relative to that at DC, and increases with increasing frequency in the measured frequency range.

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“…This non-linearity arises as a result of the quantum mechanical resonant tunnelling [51] of electrons/holes through the device, even though electron operation is typically preferred due to the higher associated drift mobility, which leads to higher current density and maximum operation frequency. The precise shape of the IV characteristic depends on different factors, such as device size, material composition, epitaxial structure, and temperature [52] [53]. The NDR region is characterised by I p and I v , which are the peak and valley currents, respectively, and corresponding voltages V p and V v .…”

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“…A detailed analysis for a more exact treatment is a future subject, including, for example, the potential change due to electron accumulation in the well [67,68], photonassisted tunneling [69][70][71], and so on, or more precise quantum-mechanical analyses [72][73][74]. In fact, the experimental result of the frequency dependence of [52] slightly deviated from the above formula, although more experimental data are needed.…”

“…In our RTD structure, a deep quantum well with indium-rich InGaAs and an emitter with InAlGaAs, having a high conduction band edge, are used to reduce the bias voltage required for NDC. Figure 2 c shows an example of the measured I–V curves at various temperatures [ 52 ]. The NDC region can be seen to have unstable current fluctuation.…”

“…The measurement of the temperature dependence of oscillation characteristics has also been reported [ 52 ]. The oscillation frequency was almost constant with temperature, while the output power drastically increased with decreasing temperature between 10 and 300 K. As NDC is insensitive to temperature, as can be seen from Figure 2 c, the change in output power was attributed to the change in Ohmic loss of the antenna electrode with temperature.…”

“…Copyright (2016) Springer Nature. ( b ) Schematic I–V curve and potential profile at various bias voltages, and ( c ) an example of measured I–V curves at various temperatures [ 52 ].…”