AVS 51st International Symposium
    Semiconductors Wednesday Sessions
       Session SC-WeA

Invited Paper SC-WeA7
InAs-based Heterojunction Bipolar Transistors

Wednesday, November 17, 2004, 4:00 pm, Room 304C

Session: Narrow Gap Semiconductors
Presenter: P.W. Deelman, HRL Laboratories
Authors: P.W. Deelman, HRL Laboratories
P.D. Brewer, HRL Laboratories
D.H. Chow, HRL Laboratories
K.R. Elliott, HRL Laboratories
T. Hussain, HRL Laboratories
R.D. Rajavel, HRL Laboratories
S.S. Thomas, III, HRL Laboratories
Correspondent: Click to Email
We have demonstrated the first InAs-based heterojunction bipolar transistors (HBTs) with f@sub T@ and f@sub max@ simultaneously exceeding 100GHz. Our best small-area (0.4 × 3.0 @micron@@super 2@) HBTs feature an f@sub T@ of 215GHz, a V@sub be@ of 0.35V, and a @beta@ of 60. Using similar devices, we have successfully fabricated the world’s first InAs-based integrated circuit - - - a divide-by-sixteen circuit operating at 27GHz. The divider consists of 62 transistors fabricated on a 3" wafer. The promise that HBTs nearly-lattice-matched to InAs potentially operate at higher frequencies and with lower power-delay products than current technologies motivated this work. Nevertheless, we have had to overcome several materials-related obstacles in order to achieve these results. For example, insulating substrates for the 6.1@Ao@ family of materials do not exist, and the nature of the band alignments in these materials dictate that at least one, if not all, the layers in the structure be strained. We employed two approaches to deal with the substrate issues. InAs transistors were grown by molecular beam epitaxy either on InP substrates using semi-insulating, strain-relaxed AlGaAsSb buffers or coherently on 3" InAs substrates. The latter approach required subsequent wafer bonding to sapphire carriers. Our baseline structures utilized either an InAsP or AlInAs emitter and an InAs base. For some devices, the emitter was graded to reduce strain energy. Current gain decreases for base doping levels above 1×10@super 19@ cm@super -3@; however, even with heavily Be-doped (~2 × 19 cm@super -3@) InAs bases, we obtain high @beta@ (>60). Numerical simulations provide an insight into the deleterious implications of Be diffusion, the degree of which can be manipulated through the MBE growth process. The work described in this talk was sponsored by DARPA/SPAWAR under contract number N66000-01-C-8033.