|dc.description.abstract||The main topic of this thesis is experimental low-frequency electrical noise characterization
of semiconductor devices. In particular, we concentrate on applications of the
silicon-germanium alloy (SiGe).
Low-frequency electrical noise is a sensitive measure of defects and non-idealities
in semiconductor devices, which directly or indirectly impact device performance and
reliability. Thus, it is of prime importance to be able to characterize the noise in semiconductor
We compare the low-frequency noise from poly-crystalline silicon-germanium thin
film resistors with different germanium content, film thickness and doping level. The
noise level decreases with increasing doping density. We find that the germanium content
and film thickness have little influence on the noise level. The noise was found to
stem from mobility fluctuations in the depletion region of the grains.
We compare the low-frequency noise of silicon based field-effect transistors with
poly-crystalline gates, made from silicon and silicon-germanium. The output noise
level for N-MOSFETs is independent of the gate material, whereas for P-MOSFETs the
silicon-germanium gate material results in lower noise. Analysis of fluctuating physical
quantities, points towards mobility fluctuations for P-MOS, and number fluctuations
We present results from measurement of the low-frequency electrical noise in Al-
GaInP QuantumWell Lasers. Experimental evidence of a connection between the noise
and device reliability is found, and hence, low-frequency noise measurements can be
used as a non-destructive reliability indicator for laser diodes.
The low-frequency noise in state-of-the-art silicon-germanium Heterojunction Bipolar
Transistors (HBTs) is explored. Device geometrical down-scaling induces a deviceto-
device noise variation, caused by small sets of noise generating traps, that are different
from device to device. We use proton irradiation to introduce additional traps, and
find that it can reduce the noise variation without increasing the noise level significantly.
Aggressive down-scaling normally results in higher low-frequency noise. However,
we find that the latest generation of SiGe HBTs (> 200 GHz) breaks this trend, and only
a residual background noise remains, resulting in record values of low-frequency noise
level and noise corner frequency.
We present, and apply, recent statistical tools to probe for non-linear coupling between
frequency components in a noise signal. These tools are applied to low-frequency
noise time series with Random Telegraph Signal (RTS) noise from small geometry SiGe
HBTs. The noise in small HBTs is shown to be non-Gaussian and non-linear. The nonlinearity
is shown to originate from the RTS component of the noise.||en