The intensity noise of light generated by semiconductor lasers and light-emitting diodes is treated by semiclassical Langevin equations. An independent equation for the junction voltage dynamics is considered, and the non-Markoffian nature of the pump current is decomposed into Markoffian carrier injection and a regulation mechanism due to charging effect at the junction. The intensity noise power spectrum and squeezing bandwidth predicted by these equations agree well with recent experimental results. External current noise generated as a result of the internal noise process and subsequent relaxation process is calculated. Also, correlations between the carrier-number fluctuation and the junction-voltage fluctuation, and between the emitted photon flux fluctuation and the junction-voltage fluctuation are studied in detail.