Statistical analysis of aging-induced degradation (or lifetime) variation in (Al, Ga)As/GaAs double-heterostructure lasers

Aging-induced degradation, defined as optical power decrease during constant current aging, is obtained for a number of (Al, Ga)As double-heterostructure lasers taken from sixty routinely grown wafers (20-30 devices per wafer). These aging characteristics are statistically analyzed wafer by wafer in correlation with initial laser parameters (or initial operating condition), i.e., CW threshold current, differential quantum efficiency, electrical resistance, nominal temperature sensitivity of threshold current, lasing wavelength, and driving current at aging. The multiple factor analysis evolved during this study reveals that degradation in average lasers can be substantially correlated to a new composite parameter defined as a linear combination of the above parameters. This fact suggests the feasibility of statistical estimation of laser degradation utilizing only the initial parameters. Of the parameters employed, driving current is revealed to be most strongly and commonly associated with laser degradation. To understand the role of driving current in causing lifetime scatters between individual lasers, a possible local heating model is developed. The lifetime scatters experimentally observed are well explained using this model.