Noncontact photothermal radiometric deep-level transient spectroscopy of undoped semi-insulating GaAs

We introduce photothermal radiometric deep-level transient spectroscopy (PTR-DLTS) as a novel noncontact defect characterization technique For semiconductor materials. By using a conventional rate window; method employed in capacitance DLTS, the near infrared emission in the wavelength range of lambda = 2 - 14 mu m from semiconductor samples is monitored as a function of temperature. The PTR-DLTS spectrum will reveal the defect as a peak at a certain temperature For a given laser beam pulse repetition period. Results from both untreated and passivated undoped semi-insulating GaAs samples suggest a surface-acceptor-dominated mechanism. Possible bulk processes are ruled out since ii the thickness of passivating layer is in submicrometer; 2) EL2-controlled processes will give a much longer time constant than what was observed from PTR-DLTS transient signals; and 3) excitation photon energy is about 2.4 eV. However, it may be possible that a tunable light excitation will reveal surface and bulk electronic properties by appropriately separating their PTR-DLTS transient signals.