NORMAL-INCIDENCE TE INTERSUB-BAND TRANSITIONS

Normal-incidence operation, based on TE electron intersub-band transit ions in n-type unipolar optoelectronic devices, would have a wide rang e of applications. However, TE intersub-band transitions are generally accepted to be (nearly) forbidden in direct gap conduction-band quant um wells, The paper describes 14-band k.p effective mass theory calcul ations of TE electron intersub-band matrix elements in n-type, direct- gap systems, to determine the extent to which TE intersub-band transit ion strengths can be enhanced by choice of quantum well shape and comp osition, The possibility of enhanced TE:TM transition strength ratios, owing to remote-band contributions to the matrix elements, is describ ed but no significant enhancement of matrix elements over predictions of the single-band model is calculated for conventional quantum wells. A mechanism is presented for nonsquare wells which is suggested to en hance TE:TM transition strength ratio based on remote-band coupling ef fects through bulk momentum matrix elements P-1 and Q.