The Study On Reliability Of Quantum Well Lasers

With the rapid development of opto-electronic technique, semiconductor lasers (LDs) are widely used in optical fiber communication, optical sensor, information memory, medical treatment and pumping solid lasers. Semiconductor laser has many advantages. Except for small volume, light weight, high conversion efficiency, the manufacturing processing of semiconductor laser is compatible with the production process of the semiconductor electron device and integrate circuit. So semiconductor laser is easy to realize the monolithic photoelectron integration with other device. The center frequency of the semiconductor laser could be tuned in wider range. The power and frequency of the semiconductor laser could be modulated expediently and efficiently and its modulation bandwidth is large. With the advance of performance of semiconductor laser, its application field has been increasingly expanded. Long-term operating of device is of crucial importance to its use in various fields. Prolonging the working life of semiconductor laser, improving the performance of device si very interesting work. So the reliability study of semiconductor laser is always a hotspot. The research on reliability and law of semiconductor laser plays a very important role in the ameliorating device performance, increasing device lifetime and the exactly use of device. Nowadays the method we use for reliability estimation and screening of semiconductor laser is electrical aging. At the process of electrical aging, the device will be heated, impacted, so, the lifetime of device will be shorten. At the long electrical aging course, if some fortuitous event happened, such as system crash or outrage, device will be spoiled in batch. Furthermore electrical aging is insensitive to the latent defect of device. For example, some devices that are eligibility in electrical aging would be rapid lapse in use. So that how to prepare high reliability device, how to analysis the factor which impact the device reliability and how to screen out the disqualification device (include the device which has latent defect) rapidly, non-destructive and conveniently is an important problems. In this paper, we use two new methods which are electrical derivative technology and noise measurement technology to research and analysis the reliability of semiconductor lasers. The main contents of this paper are shown bellow: 1.The reliability of semiconductor laser is discussed synthetically. Including the factors that impact the reliability of semiconductor laser, the degenerate mechanism and style of device. We give some methods that are used to improve device reliability at the aspect of device manufactering, technology and test. 2.The effect of temperature on laser parameters is researched. As the temperature increasing, threshold current increases. Output optical power and slope efficiency decrease as parabola and indices. At the same time characteristic temperature deceases too. 3. Electrical derivative technology is used to study semiconductor laser reliability; the relationship between electrical derivative and device characteristic and reliability is researched. We analysis and estimate the device reliability by electrical derivative parameters. By conductance number testing and aging experiment with some 50 devices, we ascertain that: to Ga/As high power single quantum well semiconductor lasers, the device (m>2.8,b>50mv,h<20mv) is of certainty disqualification, but the device (m<2.8,b<50mv,h>20mv)is of certainty qualification. 4. Noise in semiconductor lasers is used as a diagnosis tool for device quality and reliability. We do different treatments for facet surface, such as passivation, HF etching, Na+ contamination. The noise and V-I characteristic are measured before and after facer treatments. After facet treatments, the noise and V-I characteristic of the devices operating in low injection change evidently, which indicate that the noise level in device operating in low current is mainly caused by the surface component level of the current, and has closely relation with device quality. So the noise level in device operating in low current can be used to estimate the stability of device facet, which is a fast, nondestructive method. The effect of surface state, interface state, stress, temperature, defects on noise is discussed. And generating mechanisms of noise is analyzed. 5.The noise level in device operating in low bias current (I=20μA, the device operating in un-conducting state) is used as a criteria for reliability screen of semiconductor lasers, which improves the screen accuracy. One of important factors that affect device quality and reliability is stability of facet. If there are defects enhancing surface recombination at facet, the device will degrade rapidly.Other factors such as the defects in active region, the imperfect of pn junction, are also important factors affecting device reliability. On the other hand, the imperfect in waveguide layer, cap layer and ohm contact layer is also relate closely with device quality. And all these factors contribute to device noise level. Defects level in facet and active region is related with the noise level(Sv1) of device operating in low bios current, while the imperfect in waveguide layer, cap layer and ohm contact layer is related with the noise level(Sv2) of device operating in higher bias current.. So when noise is used as device reliability screen, both Sv1 and Sv2 should be considered. The noise measuring and aging results of 70 semiconductor lasers confirm that Sv1 is very important for improving screen accuracy.