An ensemble Monte Carlo (EMC) simulator has been used to study bipolar transport in siliconp+nandpn+homojunctions under forward-bias conditions, both in low- and high-injection regimes. The study focuses on a microscopic analysis of voltage fluctuations in such devices. The method of voltage-noise operation mode provides spatial analysis of the spectral density of voltage fluctuations under constant-current conditions. In the low-frequency range, the presence of shot, thermal, and excess noise due to hot carriers was found when the bias conditions were modified. Also, the EMC method permits ready evaluation of the noise equivalent temperature in both structures from the observed voltage fluctuations. ©1997 American Institute of Physics.