BARITT stands for Barrier Injection and Transit Time. The BARITT dio
de is a new class of microwave solid state devices. In this thesis
the static and microwave performances of various BARITT structures
have been studied theoretically and experimentally.
The BARITT diode family includes two types, the Schottky-type struct
ures and the pn junction-type structures. For the Schottky-type BARI
TT diodes, four structures are analyzed herein to understand their
static current-voltage. characteristics and small-signal impedance
in order to optimized for higher operation efficiency and power outp
ut. The four diode structures are Mvnp, Mnp, MvnvM and MnvM, where M
stands for metal and v for low-doping n type semiconductor. For the
pn junction-type BARITT diodes, the current transport mechanisms and
the small-signal impedance of reach-through p+np+ and its related
structures have also been studied.
The following results have been obtained:
(1) It has been established that for both types of BARITT diodes, the
current increases edponentially with voltage by thermionic injection
of carriers over the forward biased barrier (or junction) when the
applied voltage is slightly greater than the reach-through voltage,
at which the middle semiconductor region is completely depleted; whe
n the injected carrier density rises to a level comparable to the ba
ckground impurity density the space-charge-limited (SCL) effect caus
es the current to vary less rapidly with the applied voltage.
(2) General expressions for the flat-band voltage, the current-volta
ge, the current-voltage relation and the differential conductance eq
uations have been obtained which can be applied to all kinds of BARI
TT structures.
(3) For the Schottky-type BARITT diodes the differential conductance
is inversely proportional to the doping adjacent to the forward-bias
ed contact, hence the insertion of a v layer between the Mn contact
can significantly increase the conductance, the operating bias volta
ge. The SCL effect due to high injection current can generally be re
duced by replacing the reverse-biased nM or vM contact with a np jun
ction. Hence the Mvnp structure has a relatively larger conductance,
lower operating voltage and higher operation efficiency.
(4) In the small-signal analysis the drift region is separated into
a low field region and a saturated-velocity region. The theoretical
small-signal impedance equation is applicable to various structures
of the BARITT family.There is good agreement between experimental
results and the theoretical small-signal analysis.
(5) A phase delay of the injection current in the drift region of
180 is required to give rise to a suitable value of negative resista
nce; for maximum power output the length of the drift region should
be 0.7 Vs
operation frequency. An operation efficiency as high as 15% and a no
ise measure as low as 4 dB are predicted for BARITT diodes.
(6) The maximum microwave cw power of more than 100 mW and a operati
on efficiency of 1.5% have been obtained at 7 GHz from Mnp+ BARITT
diodes. They were made from silicon epitaxial n on p+ substrate with
epitaxial layer thickness of 6.5 um and doping concentration of 2x10
15 cm -3.

f where Vs is the scattering-limited velocity and f is the