Characterization of mid-gap states in n-type GaN with optical-isothermal capacitance transient spectroscopy

In this work, the deep level band structure of unintentionally doped n-type GaN grown by HVPE and MOVPE is demonstrated. Optical-isothermal capacitance transient spectroscopy (O-ICTS) is used to simultaneously observe thermal and optical emission processes from deep levels. The key benefit of this technique found when applied to GaN is that deep levels can be distinguished spectroscopically by their characteristic emission time constant. The O-ICTS spectra can be deconvoluted to estimate the concentrations and ionization energies of deep levels with a high degree of confidence.