Pump-Probe Solar Cell Inspection via Scanning Probe Light
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Solution Overview
Problem
Current semiconductor and photo device inspection techniques using pump-probe measurements are limited in their ability to detect photoexcited carriers generated, moving, or disappearing outside the region irradiated with pump light, leading to incomplete performance and defect evaluation.
Innovation Solution
An inspection device that irradiates semiconductor or photo devices with both pump and probe light of the same pulse period, with a scanning mechanism to cover a wider area than the pump light range, and includes a measurement delay part to adjust the probe light's arrival time relative to the pump light, allowing for the detection of photoexcited carriers' generation, movement, recombination, and disappearance across a broader area, along with an image generation part for electric field intensity distribution and a reverse bias voltage application for enhanced signal strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the probe light irradiation range is limited to the pump light irradiated region, then the measurement system remains simple, but photoexcited carriers generated, moving, or disappearing outside the pump light region cannot be detected
Solution Approach 1:
The patent extends the probe light scanning to a wide range that exceeds the pump light irradiation region in spatial coverage. By making the probe light path independently scannable across a broader area, the system detects photoexcited carriers not only within but also outside the pump light region, thereby resolving the contradiction between measurement precision and irradiation range coverage.
2Loss of information
If the probe light scans a wide range beyond the pump light region, then comprehensive carrier dynamics information is obtained, but the device complexity increases due to additional scanning mechanisms
Solution Approach 1:
The scanning mechanism is designed to serve multiple functions: it positions the probe light for comprehensive area coverage, enables temporal delay adjustment for pump-probe measurements, and facilitates detection across the entire device surface. By making the scanning mechanism multi-functional, the patent reduces overall device complexity while achieving complete carrier dynamics information.
Solution Approach 2:
The patent introduces a measurement delay part as an intermediary component that coordinates between the pump light source, probe light scanning mechanism, and detector. This intermediary manages the temporal and spatial relationships, allowing the scanning mechanism to operate efficiently without requiring complex independent control systems for each component.
3Measurement precision
If the probe light arrives simultaneously with the pump light, then the measurement system is simple, but the temporal dynamics of photoexcited carriers cannot be resolved
Solution Approach 1:
The patent implements a dynamic measurement delay mechanism that can adjust the probe light arrival time relative to the pump light. By making the delay adjustable rather than fixed, the system achieves subpicosecond temporal resolution for carrier dynamics while keeping the mechanism adaptable to different measurement requirements, thereby balancing precision and complexity.
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 more detailed inspections of semiconductor and photo devices by visualizing electric field intensity distributions and restoring temporal waveforms, providing comprehensive information on carrier dynamics and device performance or defects.
Implementation Method 1
irradiating it with pulsed laser light, thereby to inspect the semiconductor device in non-contact
Implementation Method 2
detecting an electromagnetic wave emitted from the photo device accordingly
Data Source
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AI summary
An inspecting device (100) includes: an irradiation part (12) for dividing pulsed light (LP1) emitted from a femtosecond laser (121) into pump light for measurement (LP13) and probe light for measurement (LP11), to irradiate a solar cell (9); a detection part for detecting an electromagnetic wave (LT1) emitted from the solar cell (9) in accordance with the irradiation with the probe light for measurement (LP11); and a delay part for measurement (14A) for delaying the time of arrival of the probe light for measurement (LP11) at the solar cell (9) relatively to the pump light for measurement (LP13). The irradiation part (12) is provided with a galvano mirror (125) for scanning with the probe light for measurement (LP11) a wide range (R11) which is wider than an irradiated range (pump light spot (SP13)) being irradiated with the pump light for measurement (LP13) in a solar cell (9).