Yasushi Matsui

Control of double diffusion front unintentionally penetrated from a Zn doped InP layer during metalorganic vapor phase epitaxy

Unintentional Zn diffusion during metalorganic vapor phase epitaxy causes serious damages in semiconductor devices. In this work, profiles of unintentionally diffused Zn atoms from a p-InP layer to the adjoining InP substrate during growth of the p-InP layer are measured by secondary ion mass spectrometry. Zn diffusion profiles with a double diffusion front, which is composed of a shallow front with high Zn concentration and a deep front with low Zn concentration, are investigated as an approach to controlling unintentional diffusion. Diffusion depth of each front is controlled in proportion to Zn dosage, which is proposed as a value calculated as Zn concentration without regard to saturation limit. The diffusion depth for the growth time of 60 min increases in proportion to the Zn dosage as the slope of 0.16 μm/1018 cm−3 for the shallow front and that of 0.32 μm/1018 cm−3 for the deep front at a growth temperature of 600 °C. The deep front expands two times faster than the shallow front, which is normall...

Stability of Zn doping profile in modulation‐doped multiple quantum well structure

Stability of the Zn doping profile in InGaAs/InGaAsP modulation‐doped multiple quantum well (MD‐MQW) structures grown by low‐pressure metalorganic vapor‐phase epitaxy (MOVPE) has been investigated by secondary ion mass spectrometry and transmission electron microscope with wedge‐shaped samples. Although excellent stability of Zn profile is confirmed in an as‐grown sample with modulation doping (d=3 nm CZn=1×1018 cm−3), the modulation‐doping structure diminishes after the second epitaxial regrowth of a p‐InP layer (CZn=1×1018 cm−3) carried out by either liquid phase epitaxy or MOVPE, which is applicable for buried heterostructure lasers. However, the modulation‐doping profile is successfully preserved even after regrowth of the p‐InP layer for 90 min in a sample constructed of an undoped InP clad layer instead of a p‐InP clad layer superposed on the MD‐MQW layers. A Zn diffusion coefficient in the modulation‐doped region is extremely small, having a value of less than 7×10−18 cm2/s. The maximum Zn concentr...

New structure by selective regrowth in multi-quantum well laser diodes performed by low pressure metalorganic vapor phase epitaxy

Abstract InGaAsP/InP multi-quantum well (MQW) planar buried hetero-structure (PBH) lasers which are grown entirely by metalorganic vapor phase epitaxy (MOVPE) on n-InP substrates are demonstrated. Two types of lasers, which are different in ridge shape (reentrant or non-reentrant), are investigated in respect of regrowth structure and damage at the regrowth interface. A new regrown structure constructed of a uniformly thick n-InP current-blocking layer formed on a reentrant ridge stripe is demonstrated for the first time. This structure is expected to be effective to suppress leakage current in laser operation. Furthermore, it is found that threshold current and reliability are strongly dependent on regrowth conditions. High quality regrowth interfaces are realized by optimizing regrowth thermal procedure and hole concentration of p-InP current-blocking layer. Stable laser characteristics in accelerated aging tests have been confirmed in both types of lasers.

Anomalous temperature dependence of PL characteristics in ordered InGaAsP strained layer multi-quantum well structure

Clarification of anomalous photoluminescence (PL) characteristics for InGaAsP compressively strained layer multi-quantum well (SL-MQW) structures is studied to realize highly strained SL-MQW lasers with a large number of well layers. PL characteristics such as an increase in PL linewidth and a small temperature dependence of the PL peak wavelength are observed in the SL-MQW structures in which a structure of CuPt-type atomic ordering is observed. Elimination of the ordered structure as well as reduction of the PL linewidth have been confirmed with increasing growth temperature. Although formation of an interfacial undulation (lateral modulation) between SL-MQW layers is also suppressed by the increase in growth temperature, the formation has ultimately limited the maximum strain in SL-MQW. We suggest that the anomalous PL characteristics result from generation of ordering, dominant when the growth temperature is lower, as well as from interfacial undulation, dominant in highly strained SL-MQW when the growth temperature is increased.

Bistability and intensity noise of semiconductor lasers due to weak optical feedback

It is shown theoretically that semiconductor lasers become bistable with weak optical feedback and that the intensity noise is increased by transitions between the bistable states due to steady‐state fluctuations. The bistability occurs in a narrow range of the feedback magnitude, depending on the phase of feedback light at the semiconductor facet. This is in good agreement with observed noise increase at low frequencies caused by external feedback.

Formation of InAsP layer on corrugated InP substrate by MOVPE for buried grating of DFB lasers

Characteristics of the InAsP layer formed on a corrugated InP substrate by a mass-transport mechanism have been investigated for use as the buried grating of distributed feedback (DFB) lasers, The size of the InAsP layer can be controlled by the height of the corrugation, and the arsenic composition in the InAsP layer can be controlled by the AsH/sub 3/ partial pressure. The results of TEM, EDS and PL show that InP is suitable as the buffer layer between the InAsP layer and MQW active layer. Fabricated 1.3 /spl mu/m DFB lasers which have an InAsP layer as an absorptive grating have shown low threshold current and high slope efficiency from -40-+85/spl deg/C, and high reliability has been demonstrated.

High reliable InGaAsP buried heterostructure laser diode fabricated by Cl/sub 2//N/sub 2/-RIBE and MOVPE

We have demonstrated high reliable InGaAsP/InP laser diodes (LDs) with buried heterostructure (BH) formed by Cl-based dry etching technique and metalorganic vapor phase epitaxy (MOVPE) regrowth for the first time. Active stripes are formed on n-type substrate by electron cyclotron resonance reactive ion beam etching (ECR-RIBE) with Cl/sub 2/ and N/sub 2/ mixture. After the formation of active stripes by Cl/sub 2//N/sub 2/ ECR-RIBE the etched surface is treated slightly with wet chemical etching to remove damaged layers and the active stripes are buried with MOVPE. An average threshold current decreases from 27 mA to 18.5 mA by the wet chemical treatment with good uniformity. In the aging test no degradation is observed after 5000 hrs operation at 70/spl deg/C under 10 mW APC condition. The mean time to failure (MTTF) for the operation at 70/spl deg/C is estimated to be 2/spl times/10/sup 5/ hrs.

A Novel Measurement Technique Of Loss And Facet Reflectivity For Semiconductor Optical Waveguide

We have proposed a novel technique to measure loss and facet reflectivity of semiconductor waveguides using Fabry-Perot resonance characterization. In order to obtain stable visibility of the optical transmittance, this technique has for the first time adopted a unique electro-optic effect instead of temperature-dependent Fabry-Perot resonance method. As a result, very accurate measurement has been realized as compared with those of currently available other measurement technique. Also we discussed the relation between spectral characteristics of incident light sources and waveguide parameters, and verified the conditions of this measurement to meet tight requirements of the waveguides.

Degradation of PL characteristics in strained layer multi-quantum well structure with atomic ordering structure

Clarification of the degradation mechanism of photoluminescence (PL) charac-teristics of InGaAsP compressively strained layer multi-quantum well (SL-MQW) structures on an InP substrate is studied to realize highly strained SL-MQW lasers with a large number of well layers. An unusual temperature-dependence of the PL peak wavelength is observed in the SL-MQW structure: the shift of the PL peak wavelength is reduced with change in measurement temperature. The degradation of PL characteristics is evaluated by the reduc-tion in the PL shift as well as an increase in PL linewidth and a decrease in PL peak intensity. The extent of the PL degradation increases with an increase in the number of well layers and an increase in strain. In the SL-MQW structure with degraded PL characteristics, the structure of CuPt-type atomic ordering is clearly observed for the first time in each barrier layer by high-resolution transmission electron microscope (HR-TEM) measurements. In the SL-MQW structure, neither dislocation nor three-dimensional nucleation is observed by TEM measurements. By increasing the growth temperature, elimination of the ordering structure as well as improvement in the PL characteristics have been confirmed even in the SL-MQW structure with a large amount of strain and a large number of well layers.

Rapid degradation of InGaAsP/InP laser diodes due to copper contamination

The influence of copper contamination upon rapid degradation of InGaAsP/InP buried-heterostructure laser diodes under accelerated high stress aging test is investigated, for the first time. Strong correlation between the quantity of contaminated copper in the laser diodes and the degradation of lasing characteristics is confirmed.