Tahir, F. R., and R. S. Fyath. “Theoretical Model for Heterojunction Phototransistor in Optoelectronic Switch Configurations Part 1: Optical Gain Characteristics”. Iraqi Journal for Electrical and Electronic Engineering, vol. 4, no. 1, Sept. 2008, pp. 44-53, https://doi.org/10.37917/ijeee.4.1.3.