Self Heating in InP DHBT Technology for 40 Gb/s ICs

Abstract Self heating is investigated in InP/InGaAs DHBT’s, a transistor technology well suited for 40 Gb/s IC’s. An original approach associates experiments andsimulations. InP DHBT’s are shown to heat up even if their I-V characteristics do not present a negativedifferential output conductance as GaAs HBT’s do.Their thermal resistance was found in the same range of values both using physical modeling and pulsedmeasurements coupled with electrical modeling. 1. Introduction High performance InP/InGaAs DHBT’s grown bychemical beam epitaxy (CBE) have been reported with 180 GHz f T , 185 GHz f MAX , a gain of 50 at a current density of 1x105 A.cm -2 , a breakdown voltage>5 V [1]. Thesefeatures are required for circuits found in 40 Gb/s IC’s. On the other side, the more established GaAs HBT’s are known to be subjected to self-heating. It is attributed to the GaAs poor thermal conductivity(K GaAs =0.455W.(cm.K) -1 ) and to the large thresholdvoltage of these heterostructures. In comparison, there is few information available on self heating in InP HBT’s [2-3]. Although K