Low frequency noise as a characterization tool for InP- and GaAs-based double-barrier resonant tunnelling diodes

This paper describes the application of low frequency noise measurements to study impurity states in three types of double-barrier resonant tunnelling diode (RTD). The noise in two types of RTD could be modelled as a combination of 1/ƒ and generation-recombination (G-R) components, in which the G-R noise displays characteristic shoulders in the noise spectra, owing to its lorentzian nature, and in which each shoulder has an associated amplitude A and corner frequency ƒc. Using G-R theory, we can derive the relationship ln(τT2) = (EA/k)·(1/T) - ln(Bσ), which relates the corner frequencies of the lorentzian relationships at several temperatures to the activation energy EA and the capture cross-section σ of the trap or impurity state. Therefore, by plotting ln(τT2) vs. 1/T, EA can be calculated from the slope and σ from the y intercept. For example, for the GaAs-based RTD, two traps with EA values of 135 and 200 meV, with corresponding σ values of 4 × 10−16cm2and 1.1 × 10−17cm2, were determined from noise measurements between 300 and 77 K. The third type of RTD, which had excellent current-voltage characteristics, had a lower normalized current noise spectral density than those of the other two types of RTD, and the noise was predominantly of the 1/ƒ type. Finally, some high temperature results (298–398 K) from InP-based RTDs, as well as an interpretation of the noise spectra will be presented.