Electron Traps In p-Type GaAsN Characterized by Deep-Level Transient Spectroscopy

We have used deep-level transient spectroscopy to detect traps in p-type GaAsN grown by metal-organic chemical vapor deposition. Although minority-carrier electrons are not intentionally injected into the depletion region of the measured samples, electron traps are detected in both Schottky barrier and p-n junction devices. The electron-trap signal can exist using only reverse biases duringmeasurement, and checks of series resistance and minority-carrier injection using an optical source also confirm the electron-trap signal. For dilute-nitrogen p-n junction samples, the electron trap gives the dominant signal peak. The peak's magnitude, which corresponds to trap density, correlates to amounts of nitrogen incorporated during growth and reduced open-circuit voltage during lightcharacterization. The p-type GaAsN layers have net acceptor carrier concentrations in the mid-1016 to low-1017 cm-3, as determined by capacitance-voltage profiling. The electron-trap concentration depends on the N content, but values, when traps are filled to saturation, range from 1015 to 1016 cm-3. The electron signal peak shows a shoulder peak on some samples, giving another close energylevel. The electron-trap activation energy is somewhat dependent on the trap filling time, but ranges from about 0.15 to 0.30 eV, and is usally near 0.2 eV for the largest peak when filled to saturation.