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 during measurement, 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 light-characterization. The p-type GaAsN layers have net acceptor carrier concentrations in the mid-10 ¹⁶ to low-10 ¹⁷ cm ^-3, as determined by capacitance voltage profiling. The electron-trap concentration is dependent on the N content, but values, when traps are filled to saturation, range from 10 ¹⁵ to 10 ¹⁶ cm ^-3. The electron signal peak shows a shoulder peak on some samples, giving another close energy level. 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 usually near 0.2 eV for the largest peak when filled to saturation.