Thermal limitations on the performance of GaAs low boundary field oscillators

A new approach has been used to calculate the maximum input power, based on thermal limitations, for pulsed GaAs transferred electron oscillators operating in the low boundary field (LBF), circuit-controlled modes, a regime including LSA and quenched multiple dipole modes. In contrast to the inverse device length dependence of the frequency of avalanche and transit-time oscillators, it has been established that the frequencies of LBF modes do not depend on the device length L. Thus L can be viewed as an independent parameter for optimizing device performance. Analyses of time dependent thermal response of various models of the device predict a thermal decay constant τ which is proportional to L squared. The expression for τ predicts values in agreement with our experimental results. To avoid excessive cumulative heating the pulse repetition frequency (PRF) is set equal to τ^-1; hence, L is determined for a given PRF.