GaAs-based 1.3um lasers grown by MBE

• Main Authors: Ru-Shang Hsiao, 蕭茹雄
• Other Authors: Jenn-Fang Chen
• Format: Others
• Language: en_US
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/59985410334506030686

博士 === 國立交通大學 === 電子物理系所 === 94 === The main purpose of this dissertation is to investigate quantum dot (QDs) growth mechanism and to optimize the material quality of GaAs based compound semiconductor telecommunications laser applications. Our final goal is to demonstrate high performance vertical cavity surface emitting lasers (VCSELs) at 1.3um. The other main focus are on the two laser active media InAs quantum dot and InGaAsN quantum well which emit light in the wavelength range in the widely used in the optical communications. In chapter 2, the Molecular Beam Epitaxy (MBE) technique is used to study the InAs QDs growth. Growth conditions such as V/III ratio, indium growth rate, and QDs combination layer were characterized by optical and electrical measurements. Our study on the material growth mechanism was aimed to find out the optimum QDs growth condition, for high quantum dots density and better light emitting material quality. The carrier transportation and relaxation from relaxed QDs were also investigated. Chapter 3 deals with characterization of VCSEL. To realize both fully doped InAs/GaAs QDs, InGaAsN/GaAs QW VCSELs at 1.3um is a challenging task since several problems must be overcome. To demonstrate the successful operation of these two devices is indeed a major break through in this work. We succeeded in solving such issues as semiconductor DBR reflectivity, detuning ranging, resistance of device, nitrogen solubility, and plasma damage in the course of this study. In addition, an oxide confined structure, incorporated in the VCSEL design, provides significantly better optical and electronical confinement and thus remarkably improve laser threshold current and efficiency. Therefore, several record-breaking lasers have been made. (1) Single mode lasing at 1.31 um with full width at half maximum of 450. (2) A threshold current of 26 mA equivalent an current density of 173 A/cm2. (3) External differential efficiency of 45% (0.43 W/A). (4) A characteristic temperature 85K indicating the Jth temperature stability with 20-600C range has been derived experimentally. (5)The single transverse mode and room temperature continuous wave threshold current below 1 mA are achieved. Chapter 4 demonstrates the optimal growth conditions of GaAsN and InGaAsN compound semiconductor alloys by RF plasma-assisted MBE. GaAsN and InGaAsN are two new dilute nitride alloys promising for a wide range of optoelectronic devices. RF plasma-assisted MBE technique is often applied to yield the high growth rate of these two alloys. In general RF plasma is easily affected by many control parameters. The parameters-forward and reflected RF powers, injected nitrogen flow rate, mixed As/N materials, ion defection plate, and the aperture size and holes are critical to compound semiconductor growth. Significant efforts have been made on the investigation of these factors. In addition, in order to grow high quality GaAsN and InGaAsN, the phase segregation problem can be suppressed by setting the substrate temperature, total growth rate, and nitrogen composition. Post annealing was applied to improve the material quality following low temperature growth. As a result, the PL intensity can increase by a factor of two orders of magnitude. Chapter 5 focuses on the InGaAsN/GaAs laser device characterization and design. A single mode laser operation with the Jth=22mA, different efficiency of 62%, and an output power more than 210mW. This power value is the highest value ever reports for single mode 1.3um GaAs based laser. A monolithic intra cavity contacted VCSEL with an InGaAsN/GaAs QWs active region, emitting light at 1304 nm, was fabricated by low-temperature growth MBE. The output power for this lasers with 18um oxided aperture size, an achieve more than 10 mW with an initial slope efficiency of 0.20 W/A under pulse operation, while under CW operation of 7um oxide aperture has been demonstrated the output power exceeds 1 mW with an initial slope efficiency of 0.15 W/A. Furthermore, a RT-CW single mode output power of 0.75 mW with an initial slope efficiency of 0.17 W/A and a side mode suppression ratio of 40 dB was achieved. This work successfully demonstrated low temperature MBE growth of high-quality InGaAsN/GaAs intra-cavity contacted VCSEL at 1.304um.