Measurement of avalanche multiplication of injected holds in germanium p-n-p diffused-base transistors

A three-terminal dc measurement is made of avalanche multiplication of holes injected from the emitter into the collector junction of diffused-base germanium p-n-p transistors. The method is applicable to asymmetric thin-base transistors at currents at which dc base current is independent of base width when emitter to base voltage (V
EB
) is held constant. Injected collector current and V
EB
are measured at constant emitter current as a function of collector to base voltage (V). V
EB
is measured to take base narrowing into account. Collector reverse current is balanced out. The advantages of this method over two-terminal measurements are that surface, space-charge recombination and internal field emission currents are balanced out and no a priori assumption of the form of the multiplication factor
M(V)
is needed. For collector barriers which are nearly step
n^{+}p
junctions with the p-type resistivity in the neighborhood of 1 ohm-cm, the multiplication data, which cover the range
1.05 \siml M \siml 2.0
, fit the Miller equation
M^{-1} = 1 - (V/V_{B})^{n} n = 3.2 \pm 0.2
in agreement with Miller's two-terminal measurements using alloy and grown-junction Ge transistors. The parameters V
B
from extrapolation of the present data agree within experimental error of five per cent with the collector diode breakdowns BV
CBO
measured by Miller. However, in the present measurements on diffused-base transistors, appreciable surface current multiplication occurs with the result that BV
CBO
measured at 1 ma is approximately 18 per cent less than V
B
. The absence of microplasma noise in the multiplied injected hole current indicates that multiplication occurs uniformly in the collector barrier under the emitter at least to
M = 2
.