Thermal Profiles Within the Channel of Planar Gunn Diodes Using Micro-Particle Sensors

Abstract

. (2017) Thermal profiles within the channel of planar gunn diodes using micro-particle sensors. IEEE Electron Device Letters, 38(9), pp. 1325-1327. (doi:10.1109/LED.2017 This is the author's final accepted version.There may be differences between this version and the published version. You are advised to consult the publisher's version if you wish to cite from it.http://eprints.gla.ac.uk/146304/ Abstract-The paper describes the use of a novel microparticle sensor (∼3 µm diameter) and infra-red (IR) microscopy to measure the temperature profile within the active channel (typically 3 µm length and 120 µm width) of planar Gunn diodes. The method has enabled detailed temperature measurements showing an asymmetrical temperature profile along the active width of these devices. The asymmetrical temperature profile suggests a similar behaviour in the channel current density, which may contribute to the lower than expected RF output power.

Investigation of Contact Edge Effects in the Channel of Planar Gunn Diodes

“…It was argued in [7] that the reason for the non-uniform temperature variation across the channel was uneven heating due to poor operation at the channel edge in this un-optimized device, and that should good operation exist in an optimized device, the heating would therefore be more even. Our simulations were therefore done on the assumption of good operation in an optimized device with a uniform lattice temperature of 300 K and at a bias of 1.36 V. The effect of any temperature variation, which might exist for any other reason, though out of the scope of this investigation, might also have some impact on the uniformity of the motion of the Gunn domain as there is some temperature dependence on the velocity of a domain and is another possible source of less than optimal performance of these planar devices.…”

“…Our simulations were therefore done on the assumption of good operation in an optimized device with a uniform lattice temperature of 300 K and at a bias of 1.36 V. The effect of any temperature variation, which might exist for any other reason, though out of the scope of this investigation, might also have some impact on the uniformity of the motion of the Gunn domain as there is some temperature dependence on the velocity of a domain and is another possible source of less than optimal performance of these planar devices. However frequency stability with respect to temperature is known to be extremely good in GaAs [12] and figure 2 shows the simulated variation in transit period for this size of device as a function of temperature over several hundred Kelvin amounts to a change of only 0.008ps K -1 and as such is not expected to have a significant impact on the device operation for variations even of the order of 10K as observed in the nonoptimized device in [7].…”

“…An ensemble Monte Carlo method was used to simulate the carrier transport in the studied devices with an established 2-D Ensemble Monte Carlo (EMC) transport model, details of Investigation of contact edge effects in the channel of planar Gunn diodes A Mindil, G M Dunn, A Khalid, and C H Oxley P which are given in [10], which has been validated against many similar experimentally realized devices [1][2][3][4][5][6][7][8][9][10]. As in [11] a doping notch next to the cathode contact was used to simulate the effect of the cathode contact to precipitate domain formation.…”

“…Furthermore, higher frequencies are potentially possible in planar Gunn diodes and operation in fundamental mode up to 164 GHz [2] have been demonstrated and yet higher frequencies would seem to be possible [6]. Power from these devices however has not yet reached its full potential as suggested by both simulation and an experimental investigation of the current distribution within the channel of the devices using a micro-particle IR thermal measurement technique [7]. The measured temperature profiles were found to be asymmetrical implying significantly lower current densities towards the edge of the channel.…”

Thermal Modeling of the GaN-based Gunn Diode at Terahertz Frequencies

“…As one of the excellent candidates for terahertz radiation source, Gunn diodes have attracted much attention [1][2][3][4][5][6][7][8]. Many recent researches demonstrate that the negative-differential-resistance (NDR) based GaN devices possess outstanding power performance at terahertz frequencies due to its unique electronic properties such as large band gap, high breakdown electric field, high electron drift velocity, and large NDR threshold voltage.…”