We propose and fabricate a light induced transistor using a combination of two multiple-quantum-well diodes (MQWDs) with a common n-electrode as the base. Both silicon removal and back wafer etching are conducted to obtain a suspended device architecture. The InGaN/GaN MQWD detects light only when the bias voltage is below the turn-ON voltage and can simultaneously achieve light emission and detection when it turns ON. Therefore, the light induced transistor operates with two distinct light detection modes. The excitatory postsynaptic voltages (EPSVs) are distinct due to the different decay times. Paired-pulse facilitation is experimentally demonstrated to mimic the synaptic plasticity behavior. The EPSV amplitudes are dependent on the pulse interval and pulse number.