Intrinsic modulation doping in InP-based structures: properties relevant to device applications

In this work we study device-relevant issues, such as doping efficiency and thermal stability, of recently proposed intrinsic modulation doping approa ch where intrinsic defects (P-In antisites) are used as a carrier source in stead of impurity dopants. The InP/InGaAs heterostructure designed to resem ble high electron mobility transistor (HEMT) structures, where all the laye rs were grown at a normal growth temperature 480 degrees C except for the t op InP layer which was grown at 265 degrees C, was used as a prototype devi ce. A comparison between the intrinsically doped structure with extrinsical ly doped HEMTs, which have an identical design except that the top InP laye r was instead Si-doped and was grown at 480 degrees C, reveals a high effic iency of the intrinsic doping. The thermal stability of the intrinsically d oped HEMT is examined by annealing at temperatures 400-500 degrees C releva nt to possible processing steps needed in device fabrication. The observed severe reduction of the carrier concentration after annealing performed wit hout phosphorous gas protection is attributed to the known instability of a n InP surface at T > 400 degrees C. Thermal stability of the intrinsically doped HEMT is shown to be improved by using an InP cap layer grown at 480 d egrees C. (C) 1999 Elsevier Science B.V. All rights reserved.