TY - GEN
T1 - On the origin of the Urbach rule and the Urbach focus
AU - Guerra, J. A.
AU - Montañez, L.
AU - De Zela, F.
AU - Winnacker, A.
AU - Weingärtner, R.
PY - 2013
Y1 - 2013
N2 - A simple derivation of sub-bandgap exponential tails and fundamental absorption equations ruling the optical absorption of amorphous semiconductors are presented following the frozen phonon model. We use the Kubo-Greenwood formula to describe the average transition rate for the optical absorption process. Asymptotic analysis leads to the commonly observed exponential tail as well as the Tauc expression for the fundamental absorption. We test our theoretical results with experimental absorption coefficients of amorphous Si:H, SiC:H, AlN and SiN. The validity of the Urbach focus concept is evaluated.
AB - A simple derivation of sub-bandgap exponential tails and fundamental absorption equations ruling the optical absorption of amorphous semiconductors are presented following the frozen phonon model. We use the Kubo-Greenwood formula to describe the average transition rate for the optical absorption process. Asymptotic analysis leads to the commonly observed exponential tail as well as the Tauc expression for the fundamental absorption. We test our theoretical results with experimental absorption coefficients of amorphous Si:H, SiC:H, AlN and SiN. The validity of the Urbach focus concept is evaluated.
UR - http://www.scopus.com/inward/record.url?scp=84889681924&partnerID=8YFLogxK
U2 - 10.1557/opl.2013.753
DO - 10.1557/opl.2013.753
M3 - Conference contribution
AN - SCOPUS:84889681924
SN - 9781605115139
T3 - Materials Research Society Symposium Proceedings
SP - 139
EP - 145
BT - Film Silicon Science and Technology
T2 - 2013 MRS Spring Meeting
Y2 - 1 April 2013 through 5 April 2013
ER -