Oblique-Axis Integrating Sphere Measurement for Standard PL Spectra
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Solution Overview
Problem
Existing measurement methods using integrating spheres for semiconductor wafers fail to accurately measure the standard PL spectrum due to interference from excitation light, necessitating the removal of the sample for separate measurements, which complicates the process.
Innovation Solution
A measuring device with an integrating sphere design where the excitation light and detection light axes obliquely intersect, using a separation optical element and blocking member to prevent direct detection of excitation light, allowing for standard PL spectrum measurement within the sphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the sample is placed inside the integrating sphere for measurement, then the measurement process is simplified and convenience is improved, but excitation light interferes with the detection of standard PL spectrum
Solution Approach 1:
The optical detection system is segmented into multiple detection ports on the integrating sphere. The standard PL spectrum is detected through a specific detection port that is spatially separated from the excitation light entry point, allowing simultaneous presence of sample in sphere without excitation light interference in the detection path.
Solution Approach 2:
The problem is solved by transitioning from a single-axis optical path to a multi-dimensional optical arrangement. Multiple detection ports are positioned at different spatial locations and angles on the integrating sphere, creating orthogonal or oblique detection paths that avoid excitation light while capturing emitted photons from all directions.
2Device complexity
If excitation light and detection light share the same optical path, then device complexity is reduced, but direct detection of excitation light interferes with PL spectrum measurement
Solution Approach 1:
The optical system is segmented into separate excitation and detection paths that originate from the same integrating sphere setup but diverge at different ports. This segmentation allows simple integration of the sample in the sphere while preventing excitation light from entering the detection path, eliminating interference without complex additional components.
Solution Approach 2:
The integrating sphere itself acts as an intermediary that diffuses and redistributes the excitation light throughout its interior. By positioning the detection port to detect light after it has been scattered multiple times within the sphere, the system detects only the emitted PL spectrum and not the direct excitation light, as the excitation light does not reach the detector in its original form.
3Measurement precision
If separate measurements are performed for standard PL spectrum and external quantum efficiency, then measurement accuracy is maintained, but measurement time and process complexity increase
Solution Approach 1:
The integrating sphere is designed with multiple detection ports that serve different measurement functions simultaneously. One port configuration enables standard PL spectrum measurement while another enables external quantum efficiency measurement, allowing both measurements to be performed on the same sample in the same setup without requiring separate measurement procedures.
Solution Approach 2:
The measurement process achieves continuity by maintaining the sample in a fixed position within the integrating sphere throughout both measurement types. The optical system switches between detection modes or ports without requiring sample removal or repositioning, enabling seamless transition between standard PL spectrum and external quantum efficiency measurements, thereby reducing measurement time and eliminating interruptions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate measurement of the standard PL spectrum while the sample is inside the integrating sphere, simplifying the setup and reducing interference, facilitating simultaneous measurements of external and internal quantum efficiencies.
Implementation Method 1
PL measurement is, for example, a method of measuring light emitted by recombination of electrons and holes generated by irradiating a semiconductor material with light having energy higher than a bandgap
Implementation Method 2
ODPL measurement is a method of measuring the number of photons of excitation light absorbed by a subject to be measured and the number of luminescence photons in all directions using an integrating sphere
Data Source
AI summary
A measuring device includes: an integrating sphere; an excitation optical system; a light detector; and a first detection optical system. The optical axis of the excitation light incident on the subject to be measured in the integrating sphere in the excitation optical system and the optical axis of the light to be measured that is emitted from the integrating sphere in the first detection optical system obliquely intersect with each other, the first detection optical system has an opening portion that limits a detection range of the light to be measured in the light detector, and an irradiation spot of the excitation light on the subject to be measured and the opening portion are in an optically conjugate relationship.