奈米結構光電元件之研究— 總計畫
Date Issued
2002-07-31
Date
2002-07-31
Author(s)
DOI
902215E002035
Abstract
This project has three subprojects. In the first subproject, we study the molecular beam
epitaxial growth of Sb-based materials and devices that have been gradually drawing attention
in high-speed electronics and optoelectronics. The growth conditions for GaAsSb/GaAs
heterojunctions were investigated. A semi-empirical incorporation model for Sb and As was
developed for precious composition control. Based on the results from growth condition
optimization, we have successfully fabricated a type II GaAsSb/GaAs quantum well laser
diode on GaAs substrate. The device demonstrates an emission wavelength of 1.26 mm and
a threshold current density as low as 201A/cm2 at room temperature.
In the second subproject, the evolution of self-assembled Ge quantum dots is studied.
Understanding and controlling the growth of self-assembled strained semiconductor quantum
dot (SAQD) is critical in realizing the application potential based on such nanostructure. In
particular, the metastability of SAQD needs to be clarified. Here we conduct quantitative
analysis on the shape evolution of Ge SAQDs grown on Si(100). It is found that the Ge
SAQDs evolve from pyramid to dome shape beyond a critical volume Vc. However,
coexistence of both island shapes in the neighbourhood of Vc is evident, indicating the shape
may be trapped by a metastability. This metastability of island can be explained as a
first-order phase transition, similar to the supercooling of water. With a model incorporating
both the strain energy gain and the surface energy cost, an energy barrier for the shape
transition ~3meV per atom is estimated. At the same time, the volume range of metastability
can be predicted and compared with the experimental finding. Our analysis should be
equally applicable to other systems such as III-V quantum dots(e.g. InAs/GaAs(100)).
In the third subproject, InGaAs/GaAs QDs are grown and Fabry-Perot QD laser diodes are
fabricated. At room temperature, long-wavelength lasing at 1.19 mm from QDs is
demonstrated. The threshold current density from an 8´1200 mm stripe laser diode is below
500 A/cm2. The emission wavelength from the QD ground state is around 1.28 mm, not far
from the target wavelength of 1.3mm which is of important application in fiber
communication systems.
Subjects
molecular beam epitaxy
Sb-based compound semiconductor
GaAsSb quantum
well
well
Ge quantum dot
InGaAs quantum dot laser diode
Publisher
臺北市：國立臺灣大學電子工程學研究所
Type
report
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