Shinji Matsukawa

Electrostatic-discharge-induced degradation of 1.3μm AlGaInAs∕InP buried heterostructure laser diodes

Degradation of 1.3μm AlGaInAs buried heterostructure laser diodes due to electrostatic discharge (ESD) is studied. The degradation mechanism of this material has not previously been clear and so the ESD tolerance was evaluated. Degradation occurred at 0.5 and 2.5kV for forward and reverse polarities, respectively. Because that ESD tolerance for forward polarity is insufficient for practical applications, we focused on it in analyzing the degradation mechanism. Elliptically shaped melted regions are observed in the active layer of the facet. Such regions developed inside a cavity under the application of ESD pulses. These results indicate that degradation is caused by melting due to optical absorption.

The Influence of Surface Pit Shape on 4H-SiC MOSFETs Reliability under High Temperature Bias Tests

The influence of surface pit shape on 4H-SiC double implanted MOSFETs (DMOSFETs) reliability under a high temperature drain bias test has been investigated. Threading dislocations formed two types of pit shapes (deep pit and shallow pit) on an epitaxial layer surface. The cause of the failure was revealed to be an oxide breakdown above the pit generated at the threading mixed dislocation in both pit shapes. Weibull distributions between two types of pits were different. Although the DMOSFETs on the epitaxial layer with the deep pit show longer lifetime than those with the shallow pit, the epitaxial layer with the shallow pit is suitable to estimate the lifetime of the DMOSFETs because of a linearity of the Weibull plot. The lifetime of the DMOSFETs with the shallow pit was dominated by an oxide electric field. The maximum oxide electric field required to obtain the lifetime of more than 10 years was estimated to be 2.7 MV/cm.

Failure Analysis of InP-Based Edge-Emitting Buried Heterostructure Laser Diodes Degraded by Forward-Biased Electrostatic Discharge Tests

We investigated the forward-biased electrostatic discharge (ESD)-induced degradation that is one of the important reliability issues for InP-based edge-emitting buried heterostructure laser diodes. Although it has been suggested that the degradation mechanism is related to optical damage, the detailed mechanism has not been established. Thus, we carried out failure analysis. Two elliptically shaped degraded regions, which were introduced by the first and second ESD pulses, were observed in an active layer. A peculiar chain-like degradation was created along the longitudinal axis. This degradation was caused by light absorption at an active layer. We also investigated the relationship between forward-biased ESD tolerance and an aging test. We observed a decrease in tolerance as a result of the aging test for laser diodes with cleaved facets. This decrease was sufficiently suppressed by facet coating. We identified two reasons why facet coating is important. One is to obtain sufficient ESD tolerance under initial conditions, and the other is to suppress the decrease in ESD tolerance during aging.

Current-Induced Step Bunching on Vicinal Si(111) Studied by Light Scattering

Step bunching on vicinal Si(111) surfaces induced by direct current heating has been studied using an in situ light scattering measurement system. For annealing at 1240°C, the average terrace width increased as a power of the annealing time with an exponent of 0.50±0.03 in the range of 3–14 µm. During the step bunching process, the ratio of the standard deviation of the terrace width to the average terrace width remained constant at 0.24. Light scattering in the course of debunching was also observed.

Dependence of facet stress on reliability of AlGaInAs edge-emitting lasers

The relationship between facet stress and reliability of AlGaInAs edge-emitting lasers is unclear despite it being an important issue. We prepared two 1.3 μm AlGaInAs Fabry–Perot buried-heterostructure (BH) lasers that were identical except that they had tensile and compressive stress at the facet. The magnitude of the facet stress was controlled to be approximately 200 MPa in both lasers. We performed three reliability tests. In forward-biased electrostatic discharge tests, which can evaluate the resistance to optical damage, the cumulative degradation ratio of the compressive stressed laser was 33% lower than that of the tensile stressed laser. This result indicates a reduction in the optical absorption due to enlargement of the energy band gap at the facet. In the long-term aging of the light output power of 8 mW at 85 °C over 5 000 h, no dependence of the facet stress on the lifetime was observed. Since a major limitation of InP-based BH lasers is the BH interface, the aging results are reasonable. In...

Analysis on forward-biased electrostatic-discharge-induced degradation of InP-based buried heterostructure laser diodes

We clarified the mechanism of forward-biased electrostatic-discharge-induced degradation of InP-based laser diodes. This degradation was caused by melting of the active layer as a result of light absorption. We observed a reduction in tolerance on aging in uncoated laser diodes. This reduction was suppressed by facet coating.

Improvement in electrostatic-discharge tolerance of 1.3µm AlGaInAs/InP buried heterostructure laser diodes

This is the first report on electrostatic discharge (ESD)-induced degradation of AlGaInAs/InP buried heterostructure laser diodes. We found that the dominant degradation mechanism was melting of the active layer due to light absorption. We successfully improved ESD tolerance by facet passivation. The cumulative degradation ratio at 1.0kV ESD tests was decreased from 40 to 0%.