An ultrasensitive radio-frequency single-electron transistor working up to 4.2 K

Abstract

We present the fabrication and measurement of a radio frequency single electron transistor (rf-SET), that displays a very high charge sensitivity of 1.9 µe/ √ Hz at 4.2 K. At 40 mK, the charge sensitivity is 0.9 and 1.0 µe/ √ Hz in the superconducting and normal state respectively. The sensitivity was measured as a function of radio frequency amplitude at three different temperatures; 40 mK, 1.8 K and 4.2 K.

Sensitive Radio-Frequency Measurements of a Quantum Dot by Tuning to Perfect Impedance Matching

“…3(a)]. From the height of the sidebands above the noise floor, the sensitivity is given by S C ¼ ð1= ffiffi ffi 2 p ÞδCðΔfÞ −1=2 10 −SNR=20 , where SNR is the sideband signal-to-noise ratio expressed in decibels, and Δf is the resolution bandwidth [21]. Over the range of varactor settings measured, S C is found to change by a factor > 15, with the best sensitivity close to perfect matching as expected [ Fig.…”

Highly sensitive and broadband carbon nanotube radio-frequency single-electron transistor

“…We obtain a charge sensitivity of ␦q = 2.3ϫ 10 −6 e / ͱ Hz, which is nearly as good as the best Al/ AlO x results. 9 It represents an enhancement of at least a factor of 7 compared to previous carbon nanotube rf-SETs. [15][16][17] Very recently, comparable sensitivities were achieved with other types of SETs: ͑1͒ InAs/InP heterostructured nanowires 27 and ͑2͒ electrostatically defined Si quantum dots.…”

“…30 For Al/ AlO x junction SETs, the improvements at 40 mK were ␦q = 0.9e / ͱ Hz in the superconducting state and ␦q = 1.0e / ͱ Hz in the normal state. 9 To improve the bandwidth, the only option is to increase the resonance frequency of the LC-circuit. The limit set by the Bode-Fano criterium states that the maximum achievable bandwidth is ͑2R ⌺ C͒ −1 , which in our case amounts to ϳ170 MHz.…”

“…Provided that E C eff ӷ k B T, the strong tunneling SETs are expected to operate well as rf-SETs. 8 This regime of operation has been strived for by Brenning et al 9 They managed to fabricate Al/ AlO x tunnel junction SETs with E C / k B = 18 K and a total resistance of R ⌺ =25 k⍀. For the charge sensitivity, they reached ␦q = 1.9 ϫ 10 −6 e / ͱ Hz at 4.2 K, which is the best liquid helium result obtained so far.…”

Overall performance evaluation using an equivalent circuit model for radio-frequency single-electron transistors

“…3,4 In the so-called sequential tunneling regime, the blockade can be lifted and electrons may tunnel one-by-one through two small tunnel junctions under the control of a gate electrode, which couples to the SET island via a capacitance C g . As such the device current can be modulated periodically by a gate voltage with a period, V g = e/C g .…”