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In this work, by means of Monte Carlo simulations, the static and dynamic behavior of isolated-gate InAs/AlSb high electron mobility transistors (Sb-HEMTs) has been studied and compared with experimental results. The influence of the existence of a native oxide under the gate, the value of the surface charges in the gate recess and the possible variation of electron sheet carrier density, ns, has been studied. A decrease in the gate-source capacitance, transconductance and intrinsic cutoff frequency is observed because of the presence of the native oxide, while changes in the value of the surface charges in the recess only introduce a threshold voltage shift. The increase of ns shifts the maximum of the transconductance and intrinsic cutoff frequency to higher values of drain current and improves the agreement with the experimental results.

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A semiclassical two-dimensional ensemble Monte Carlo simulator is used to perform a physical analysis of the kink effect in InAs/AlSb high electron mobility transistors ͑HEMTs͒. Kink effect, this is, an anomalous increase in the drain current I D when increasing the drain-to-source voltage V DS , leads to a reduction in the gain and a rise in the level of noise, thus limiting the utility of these devices for microwave applications. Due to the small band gap of InAs, InAs/AlSb HEMTs are very susceptible to suffer from impact ionization processes, with the subsequent hole transport through the structure, both implicated in the kink effect. The results indicate that, when V DS is high enough for the onset of impact ionization, holes thus generated tend to pile up in the buffer ͑at the gate-drain side͒ due to the valence-band energy barrier between the buffer and the channel. Due to this accumulation of positive charge the channel is further opened and I D increases, leading to the kink effect in the I-V characteristics and eventually to the device electrical breakdown. The understanding of this phenomenon provides useful information for the development of kink-effect-free InAs/AlSb HEMTs.