J.J.M. Kwaspen

Influence of scattering on the I-V characteristics of double-barrier resonant-tunneling diodes

The influence of incoherent tunneling in double-barrier resonant-tunneling (DBRT) diodes, originating in carrier scattering, is investigated using a previously published model in which the device is divided into three regions (accumulation region, barrier region and depletion region), each of which is analyzed by a separate model. In the barrier region a self-consistent quantum mechanical model is used. Scattering is assumed to contribute a damped amplitude to the coherent wave function and the non-coherent carriers are assumed to tunnel out through one of the two barriers in proportion to the transmittivities of the latter. The damping factor can be related to the momentum relaxation time used in transport calculations. A good match of calculated to experimental I-V characteristics, measured on GaAs/AlGaAs DBRTs, can be obtained using a scattering time constant substantially shorter than that of bulk GaAs, indicating that there are extra scattering mechanisms to take account of.

Automatic display of electron density in a plasma column

A method is described to obtain a voltage proportional to the average electron density in a gas discharge tube of small diameter. The method is based on the well known cavity method. The cavity in which the plasma column is placed is inserted in a feedback circuit known as the Pound stabilization circuit, which was originally devised as a means to stabilize the output frequency of a microwave oscillator on the resonant frequency of a cavity. In the method described here, the oscillator frequency is made to follow the cavity resonant frequency. The voltage which controls the oscillator frequency is made to vary linearly with the frequency and hence with the electron density.

Microwave analysis of double barrier resonant tunneling diodes

Accurate microwave measurements up to 40 GHz have been carried out on GaAs/AlAs Double Barrier Resonant Tunneling (DBRT) diodes over the whole bias range of its DC characteristic. The resulting small-signal scattering parameters (S-parameters) have been analysed afterwards in terms of equivalent circuits. The analysis demonstrates that the most suitable equivalent circuit of the DBRT structure has to include, apart from the circuit elements used to model the Esaki tunnel diode, an intrinsic inductance which is related to the life time of the quantum well quasi-state involved in the tunneling process. The bias dependency of the equivalent circuit parameters and the maximum oscillation frequency of the DBRT device have been obtained.

Microwave noise behaviour of resonant tunnelling diodes

A method to measure the microwave noise properties of double barrier resonant tunnelling (DBRT) diodes is described. The noise figure and noise measure of (nonoscillating) DBRT diodes were measured over the full positive and negative bias voltage range, in the 1-1.6 GHz frequency band. The results classify DBRT diodes as low noise devices.

Microwave Noise Behaviour of Double Barrier Resonant Tunnelling Diodes

A method to measure the noise properties of double barrier resonant tunnelling (DBRT) diodes is described. The noise figure and noise measure of (nonoscillating) DBRT devices were measured over the full positive and negative bias voltage range, in the 1-1.6 GHz frequency band. Results show a clear bias dependence and almost frequency independence. The lowest noise measure observed on a 16 ¿m mesa DBRT diode biased in its active regions was 3, indicating that DBRT diodes are low noise devices.