Measurement and Interpretation of Long Spontaneous Lifetimes in Double Heterostructure Lasers

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Abstract
From measurements of stimulated emission time delays, values of the spontaneous carrier lifetime at the lasing threshold for double heterostructure (DH) lasers have been determined in the temperature range 77–400°K. Typical lifetime values are found to decrease from 10 to 15 nsec at 77°K to about 2–4 nsec near 400°K. These lifetimes are longer by factors of 3 and 6 than in single heterostructure (SH) lasers and homostructure (diffused) lasers, respectively. It is shown theoretically that this increased lifetime alone contributes to lowering the threshold current density for DH lasers by about a factor of 2. It is also shown how the long delay times can be reduced by prepumping the laser in order to increase the maximum allowable repetition rate in pulsed operation. Finally, it is suggested that the longer lifetime values in DH lasers are a result of the growth conditions used to form the Si‐doped active regions. These conditions produce a high degree of compensation in DH lasers which is not present in the diffused active regions of either SH or homostructure lasers.