Manufacturability and reliability of InP HEMTs

This article describes the present status concerning manufacturability and reliability of InP HEMTs (n-AlInAs/InGaAs/InP HEMTs) towards the practical use. The precise and reproducible control in the gate recess etching for the InP HEMTs was realized by employing the highly selective pH-adjusted citric acid based solution. The 0.15 mu m-length T shaped gate InP HEMT fabricated on 3 inch wafers by the selective recess etching showed a minimum noise figure as low as 0.9 dB with an associated gain of 7.0 dB at 60 GHz and a standard deviation in I-dss as low as 3.2 mA. These successful results promise the good manufacturability of the excellent performance InP HEMTs with high yield. The present reliability of the InP HEMTs is at least one order lower than that of conventional GaAs based HEMTs because of their poor thermal stability. It is demonstrated that the main reason for the thermal instability of the InP HEMTs originates from the donor passivation in the n-AlInAs electron supplying layer caused by fluorine during the thermal stress and that this donor passivation is peculiar to the materials containing both AlAs and InAs. The mechanism of this peculiar donor passivation and some ideas for the suppression of it is discussed. (C) 1997 Elsevier Science Ltd.