Physics of breakdown in InAlAs/InGaAs MODFETs - Device Research Conference, 1993. 51st Annual

InAlAsLlnGaAs MODFETs have achieved record high-frequency and low-noise performance. They are promising candidates for applications in microwave and lightwave communication systems. Their main weakness, however, has been their low breakdown voltage (BV) which severely limits their applications. Considerable work has focussed on improving BV of these devices. Recently, BV up to 10 V has been demonstrated [ 11 by using a combination of surfacedepleted InGaAs cap, mesa-sidewall isolation, and SisN4 passivation layer. These devices offer a unique opportunity to explore the intrinsic physics of breakdown and assess the ultimate potential of InAlAs/InGaAs MODFETs for power applications. In this abstract, we present a detailed study of the physics of off-state breakdown in state-of-the-art lattice-matched and pseudomorphic InA1As/InGaAs MODFETs. We find that, similarly to heterojunction avalanche photodiodes, breakdown in these devices is a two-step process. First, electrons are injected from the gate into the channel through thermionic-field emission. Second, because of the large conduction-band offset and the electric-field in the insulator, these electrons enter the channel hot and immediately relax their energy through impact-ionization. Both steps are important in the breakdown process.