Detection of ionizing radiation with modulation doped field effect transistors (MODFETs) is provided. There are two effects which can occur, separately or together. The first effect is a direct effect of ionizing radiation on the mobility of electrons in the 2-D electron gas (2DEG) of the MODFET. An ionizing radiation absorption event in or near the MODFET channel can perturb the 2DEG mobility to cause a measurable effect on the device conductance. The second effect is accumulation of charge generated by ionizing radiation on a buried gate of a MODFET. The conductance of the MODFET can be made sensitive to this accumulated charge, thereby providing detection of ionizing radiation. 1-D or 2-D arrays of MODFET detectors can be employed to provide greater detection area and/or spatial resolution of absorption events. Such detectors or detector pixels can be integrated with electronics, such as front-end amplification circuitry.