Modulated and Fourier-transformed transient photocurrent (MPC and TPC-FT) spectroscopies have been evaluated through a study of the density and capture properties of localised states in as-prepared and light-soaked PECVD a-Si:H samples over a range of temperatures and optical excitations. Both techniques return a conduction band tail state characteristic energy of approximately 22 meV. However, defect state spectra differ in detail and are strongly influenced by dc optical excitation. A feature correlating with the quasi-Fermi level position is observed, but the capture coefficient implied (of order 10-6 cm3 s-1) is some two orders greater than that calculated from thermal activation of emission frequencies. Such a value would suggest an implausibly low absolute density of defects. Possible explanations are briefly discussed and additional investigations proposed.
|Title of host publication||Amorphous & Heterogeneous Silicon Thin Films - 1999|
|Editors||H. M. Branz, R.W. Collins, S. Guha, H. Okamoto, R. Schropp|
|Publisher||Materials Research Society|
|Publication status||Published - 1999|
|Name||MRS Symposium Proceedings Series|
Reynolds, S., Main, C., Webb, D. P., & Rose, M. J. (1999). An experimental evaluation of modulated photocurrent spectroscopy as a density of states probe. In H. M. Branz, R. W. Collins, S. Guha, H. Okamoto, & R. Schropp (Eds.), Amorphous & Heterogeneous Silicon Thin Films - 1999 (Vol. 557). (MRS Symposium Proceedings Series; Vol. 557). Materials Research Society. https://doi.org/10.1557/PROC-557-427