LED based avalanched photodetector - Revision history

Runzhi: /* Calculation of quenching equivalent capacitance circuit */

2025-04-29T10:23:58Z

Calculation of quenching equivalent capacitance circuit

← Older revision		Revision as of 18:23, 29 April 2025
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	:Where ε is the dielectric constant of the material, <math>V_{bi}</math> is the built-in electric field voltage, <math>N_{A}</math> and <math>N_{A}</math> is the charge carrier density in P and N zone. Simplifying the formula with approximate carrier density <math>N_{0}=\frac{N_{A}N_{D}}{N_{A}+N_{D}}</math>, we can obtain:		:Where ε is the dielectric constant of the material, <math>V_{bi}</math> is the built-in electric field voltage, <math>N_{A}</math> and <math>N_{A}</math> is the charge carrier density in P and N zone. Simplifying the formula with approximate carrier density <math>N_{0}=\frac{N_{A}N_{D}}{N_{A}+N_{D}}</math>, we can obtain:
	<div style="text-align:center;"><math>C_{LED}=\frac{\varepsilon S}{W}=S\sqrt{\frac{\varepsilon eN_{0}}{2(V_{bi}-V_{LED})}}</math></div>		<div style="text-align:center;"><math>C_{LED}=\frac{\varepsilon S}{W}=S\sqrt{\frac{\varepsilon eN_{0}}{2(V_{bi}-V_{LED})}}</math></div>
	:Since the capacitance is a non-linear function of V_LED, it is extremely difficult to solve the circuit equation directly; instead, translating the equation into numerical calculation programme in MATLAB makes it easier to visualize the theoretical calculation result, which is ~~similar~~ to experimental results:		:Since the capacitance is a non-linear function of V_LED, it is extremely difficult to solve the circuit equation directly; instead, translating the equation into numerical calculation programme in MATLAB makes it easier to visualize the theoretical calculation result, which is relatively close to experimental results:
	<div style="text-align:center;">[[Image:Quench time 2.png\|400px]]		<div style="text-align:center;">[[Image:Quench time 2.png\|400px]]

Runzhi: /* Group members: */

2025-04-29T10:05:38Z

Group members:

← Older revision		Revision as of 18:05, 29 April 2025
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	==~~'''~~Group members:~~'''~~==		==Group members:==

	Cai Shijie		Cai Shijie

Runzhi: /* Group members: */

2025-04-29T10:05:25Z

Group members:

← Older revision		Revision as of 18:05, 29 April 2025
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	=='''Group members:'''==		=='''Group members:'''==

	Cai Shijie ~~Email:E1184418@u.nus.edu.sg~~		Cai Shijie

	~~Nie Huanxin~~ Email: ~~E1352877~~@u.nus.edu.sg		Email:E1184418@u.nus.edu.sg

	Yang Runzhi Email:E1127408@u.nus.edu.sg		Nie Huanxin

			Email: E1352877@u.nus.edu.sg

			Yang Runzhi

			Email:E1127408@u.nus.edu.sg

	== Idea ==		== Idea ==

Runzhi: /* Group members: */

2025-04-29T10:04:54Z

Group members:

← Older revision		Revision as of 18:04, 29 April 2025
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	=='''Group members:'''==		=='''Group members:'''==

	Cai Shijie Email:E1184418@u.nus.edu.sg		Cai Shijie Email:E1184418@u.nus.edu.sg

	Nie Huanxin Email: E1352877~~@u.nus.edu.sg~~		Nie Huanxin Email: E1352877@u.nus.edu.sg

	~~Yang Runzhi Email:E1127408~~@u.nus.edu.sg

			Yang Runzhi Email:E1127408@u.nus.edu.sg

	== Idea ==		== Idea ==

Runzhi: /* Group members: */

2025-04-29T10:04:28Z

Group members:

← Older revision		Revision as of 18:04, 29 April 2025
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	='''Group members:'''=		=='''Group members:'''==

	Cai Shijie Email:E1184418@u.nus.edu.sg		Cai Shijie Email:E1184418@u.nus.edu.sg
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	=== Idea ===		== Idea ==

	Our project aims to construct a photo detector to measure some phenomena in optical experiment. We choose Poisson distribution of photons generated by LED as our target phenomena. In the sensor part, we want to detect number of photons, thus we choose reversed LED as the sensor. Using avalanche effect in LED, we could detect relative number of photons with observable quantities.		Our project aims to construct a photo detector to measure some phenomena in optical experiment. We choose Poisson distribution of photons generated by LED as our target phenomena. In the sensor part, we want to detect number of photons, thus we choose reversed LED as the sensor. Using avalanche effect in LED, we could detect relative number of photons with observable quantities.
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	In the main part, we constructed this LED based avalanched photodetector(APD), explained the working principle and analyzed the result detected by the LED based APD, especially compared the distribution results of photon with theoretical Poisson distribution.		In the main part, we constructed this LED based avalanched photodetector(APD), explained the working principle and analyzed the result detected by the LED based APD, especially compared the distribution results of photon with theoretical Poisson distribution.

			==Main==
	=== Part 1. Working Principles: ===		=== Part 1. Working Principles: ===
	'''Author: Nie Huanxin'''		'''Author: Nie Huanxin'''

Runzhi at 10:03, 29 April 2025

2025-04-29T10:03:41Z

← Older revision		Revision as of 18:03, 29 April 2025
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	'''Group members:'''		='''Group members:'''=

	Cai Shijie Email:		Cai Shijie Email:E1184418@u.nus.edu.sg

	Nie Huanxin Email: E1352877@u.nus.edu.sg		Nie Huanxin Email: E1352877@u.nus.edu.sg

Runzhi: /* Part 1. Working Principles: */

2025-04-29T10:03:07Z

Part 1. Working Principles:

← Older revision		Revision as of 18:03, 29 April 2025
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	=== Part 1. Working Principles: ===		=== Part 1. Working Principles: ===
	'''~~Editor~~: Nie Huanxin'''		'''Author: Nie Huanxin'''
	==== Avalanche Photon detection of Reverse-biased LED ====		==== Avalanche Photon detection of Reverse-biased LED ====
	:When a light-emitting diode (LED) light bulb is forward-biased,electrons from the n-region and holes from the p-region migrate toward the depletion zone under the applied electric field. Upon recombination in the active region, energy is released as photons via radiative recombination of charge carriers, converting electrical energy into light—the fundamental principle of LEDs. However, under reverse bias <math>V_{re}</math>, the LED operates as a photodetector: In the absence of incident photons, the depletion region in LED widens and the built-in electric field is strengthened. Although minority carrier diffusion increases, the absence of photogenerated free carriers results in negligible current (limited only by intrinsic thermal generation). When photons with energy exceeding the bandgap (ℎ𝜈 ≥ 𝐸𝑔) are absorbed, electron-hole pairs (EHPs) will be generated within the depletion zone and separated by strong built-in electric field, then the reverse-biased LED light bulb will operates as a photodetector with distinct voltage-dependent response regimes:		:When a light-emitting diode (LED) light bulb is forward-biased,electrons from the n-region and holes from the p-region migrate toward the depletion zone under the applied electric field. Upon recombination in the active region, energy is released as photons via radiative recombination of charge carriers, converting electrical energy into light—the fundamental principle of LEDs. However, under reverse bias <math>V_{re}</math>, the LED operates as a photodetector: In the absence of incident photons, the depletion region in LED widens and the built-in electric field is strengthened. Although minority carrier diffusion increases, the absence of photogenerated free carriers results in negligible current (limited only by intrinsic thermal generation). When photons with energy exceeding the bandgap (ℎ𝜈 ≥ 𝐸𝑔) are absorbed, electron-hole pairs (EHPs) will be generated within the depletion zone and separated by strong built-in electric field, then the reverse-biased LED light bulb will operates as a photodetector with distinct voltage-dependent response regimes:

Runzhi: /* Part 2. Experimental Setup */

2025-04-29T10:02:51Z

Part 2. Experimental Setup

← Older revision		Revision as of 18:02, 29 April 2025
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	=== Part 2. Experimental Setup ===		=== Part 2. Experimental Setup ===
	'''~~Editor~~: Yang Runzhi'''		'''Author: Yang Runzhi'''

	==== Equipment and the circuit====		==== Equipment and the circuit====

Runzhi: /* Part 3. Results and Analysis */

2025-04-29T10:02:39Z

Part 3. Results and Analysis

← Older revision		Revision as of 18:02, 29 April 2025
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	=== Part 3. Results and Analysis ===		=== Part 3. Results and Analysis ===

	'''Author: Cai Shijie ~~Email:e1184418@u.nus.edu.sg~~'''		'''Author: Cai Shijie'''
	'''Date: April 2025'''		'''Date: April 2025'''

Runzhi: /* Part 2. Experimental Setup */

2025-04-29T10:02:22Z

Part 2. Experimental Setup

← Older revision		Revision as of 18:02, 29 April 2025
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	=== Part 2. Experimental Setup ===		=== Part 2. Experimental Setup ===
	'''~~Author~~: Yang Runzhi'''		'''Editor: Yang Runzhi'''

	==== Equipment and the circuit====		==== Equipment and the circuit====