研究目的
To analyze the interface roughness of Al0.56Ga0.44N/Al0.62Ga0.38N multiquantum wells grown by MBE by studying the optical properties and structural characteristics of the quantum wells with internal quantum efficiency (IQE) ~30%.
研究成果
The interface roughness of the AlGaN MQWs was estimated to have an average height of 0.3-1nm, with good agreement between calculated and measured values. The increase in radiative lifetime with temperature indicates that luminescence originates from confined states at the interfaces, influenced by electron-hole scattering.
研究不足
The study assumes pseudomorphic growth and uses specific models that may not account for all variables. Interface roughness might be more severe for quantum wells emitting at shorter wavelengths, and challenges in heteroepitaxy with high Al compositions could affect results.
1：Experimental Design and Method Selection:
The study involved growing AlGaN multiquantum wells using plasma-assisted molecular beam epitaxy (PA-MBE) under Ga-rich conditions on AlN-on-sapphire templates. Methods included photoluminescence (PL), transmission and reflectance spectroscopy, and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) to characterize optical and structural properties.
2：Sample Selection and Data Sources:
Samples consisted of Al0.56Ga0.44N/Al0.62Ga0.38N MQWs and single AlGaN layers with identical compositions grown on AlN-on-sapphire templates. Data were obtained from these samples using various measurement techniques.
3：56Ga44N/Al62Ga38N MQWs and single AlGaN layers with identical compositions grown on AlN-on-sapphire templates. Data were obtained from these samples using various measurement techniques. List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: Equipment included a Veeco Gen 930 PA-MBE system for growth, a frequency-tripled Ti:sapphire laser for PL excitation, a 0.75m monochromator with PMT detection, a closed-cycle helium cryostat for temperature control, a thermoelectrically-cooled fast hybrid photomultiplier tube for time-resolved PL, a variable-angle spectroscopic ellipsometer for reflectance and transmission measurements, and HAADF-STEM for structural imaging. Materials included AlN templates on sapphire, Al and Ga sources for MBE.
4：75m monochromator with PMT detection, a closed-cycle helium cryostat for temperature control, a thermoelectrically-cooled fast hybrid photomultiplier tube for time-resolved PL, a variable-angle spectroscopic ellipsometer for reflectance and transmission measurements, and HAADF-STEM for structural imaging. Materials included AlN templates on sapphire, Al and Ga sources for MBE. Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Growth was performed at specific temperatures (880°C for AlN buffer, 780°C for subsequent layers) with controlled fluxes and interruptions to remove excess Ga. PL measurements were conducted with excitation at 236nm, and data were collected at various temperatures and excitation intensities. Reflectance and transmission measurements were made at room temperature with specific angles. HAADF-STEM was used for cross-sectional imaging.
5：Data Analysis Methods:
Data analysis involved Gaussian fitting of PL spectra, Varshni equation for temperature dependence, stretched exponential model for time-resolved PL, and calculations using Schr?dinger equation and models for linewidth broadening due to alloy scattering and interface roughness.
独家科研数据包，助您复现前沿成果，加速创新突破
获取完整内容-
Veeco Gen 930 PA-MBE system
Gen 930
Veeco
Used for plasma-assisted molecular beam epitaxy growth of the AlGaN multiquantum wells.
-
frequency-tripled Ti:sapphire laser
Used for photoluminescence excitation at 236nm.
-
monochromator
0.75m
Used to analyze photoluminescence emission.
-
photmultiplier tube
Used for detection in photoluminescence measurements.
-
closed-cycle helium cryostat
Used for temperature-dependent photoluminescence measurements.
-
thermoelectrically-cooled fast hybrid photomultiplier tube
Used for time-resolved photoluminescence detection.
-
variable-angle spectroscopic ellipsometer
Used for reflectance and transmission measurements.
-
high-angle annular dark-field scanning transmission electron microscope
HAADF-STEM
Used for structural characterization and imaging of the quantum wells.
-
登录查看剩余6件设备及参数对照表
查看全部
