Study of the kink effect in AlInAs/GaInAs/InP composite channel HFETs

A detailed study is presented on AlInAs/InGaAs/InP composite channels. Thes e devices combine the advantages of high mobility at low voltages and high electric field operations thanks to the use of a composite channel formed b y a thin InGaAs layer and a doped InP subchannel. Due to the very low gate leakage currents, it has been possible to precisely study the impact ioniza tion contributions as a function of the temperature. Surprisingly, it is no t possible from our measurements to correlate the kink effect observed in t he devices with the impact ionization phenomenon. Therefore, a detailed stu dy of the AlInAs deep traps, and the deep levels detected in the devices ha s been performed using DLTS, CTS, drain lag, and low frequency noise measur ements. The observation of the kink effect in our HFETs has been clearly co nnected to an electron trap located in the AlInAs layers. In order to confi rm this result, the optical properties of this deep trap have been studied by I-V measurements under optical excitation for HFETs, and by DLOS on bulk AlInAs. Our measurements show that the same defect is observed in AlInAs a nd in the HFETs and that it is possible to suppress the kink effect by an o ptical ionization of this electron trap. Finally, our electro-optical study shows the direct correlation between deep traps in the AlInAs barrier laye rs and the kink effect in these devices.