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Photodetector Diodes
Marjan Alavi School of Electrical Engineering Sharif University of Technology
1
Outline Intoduction APD PIN Diodes IIMPATT Devices Applications References
2
Photodiode Basic Principle
O-E Converter The Electron-Hole Pair Give Rise to an Electrical Current Conduction Band
Electron
ΔE
Absorption
E=hc/λ Photon
Hole
Valence Band
bock-bock.cisco.com/~abarbier 3
Photodetectors P-I-N photodiodes: Intrinsic
layer of semiconductor between the p-doped and n-doped side to extend the usable area to receive photons
Avalanche Photo Diode (APD): strongly
biased (reverse biasing) pn diode that creates many electron-hole pairs per each photon received; Aplifies the signal :improved sensitivity
http://hepunx.rl.ac.uk/BFROOT/
4
General Principles The photogenerated current, Iph, increases linearly with: The
optical power Magnitude Ratio of Iph to the incident optical power, Φ: responsivity, ℜ of the photodiode.
The
5
The Ideal Photodiode All the incident light would be absorbed The quantum efficiency would then be unity Minimizing reflection at the incident surface; Maximizing the absorption within the depletion layer Avoiding recombination before the carriers are collected. 6
Basic Photodiode Configuration Good
linearity Low noise High frequency response Easy to manufacture
7
PIN Photodiode Absorptive p InP
i
n
InGaAs
InP
Optical Input
Transparent
VR bock-bock.cisco.com/~abarbier
8
Response Time CR time constant of the diode capacitance and its load Carrier transit time within the diode local recombination time Bandwidths exceeding 1GHz are practical. 9
Quantum Efficiency Quantum efficiency, η, for a given device:
the ratio between Iph, measured in electrons per second and the incident optical flux, measured in photons per second. η = Iph/e ÷ Φ/εph = (Iph/Φ).(hc/eλ) = ℜ. (hc/eλ)
10
Bandwidth Bandwidth = 1/ ttr
11
Noise
12
Singal to Noise Ratio
13
PIN Sample P+ layer: 103nm (1/4 l ) I-layer: 2µm 11(1/2 l), h=0.99 N- layer: 2µm 22(1/4 l) Responsivity: 1.04A/W Response time: 28.6 psec Minimum detectable signal: 250W/cm2 14
APD principle of operation Incident photons generate charge carriers in the depletion region Accelerated to high speeds by an applied electric field Ionize atoms within the avalanche region
http://optics.org/articles
15
APD Application High sensitivity at high-speed operation: optical
communications
http://optics.org/articles 16
APD optimum operating
point Detector's signalto-noise ratio is APDs are the preferred choice if:
light levels are limited (microwatts or nanowatts) A fast response (up to gigahertz) is required.
http://optics.org/articles
17
IMPATT Diode Impact Avalanche And Transit Time diode Operates in reverse-breakdown (avalanche) region Applied voltage causes momentary breakdown once per cycle This starts a pulse of current moving through the device Utilizes impact ionization and transfer time delay to generate negative resistance
Frequency depends on device
18
IMPATT Structure High density next to the junction reduce E from 300500 for avalanche to 15 KV/cm for Vsat in drift region P+ n n+ or P+ nin+
19
Static Characteristics High Electric field (E=3 – 6 e5 V/cm) Avalanche multiplication Generating E/H pairs Drift velocity Negative resistance
20
Satic Characteristics
with proper choice of doping and region width, avalanche region can be entirely contained within region with doping N1 21
Dynamic Characteristics Avalanche region introduces phase shift of π /2 in the injected carrier density For π<ωt<2π, carriers drift across to n+-contact Carriers will drift at saturation velocity Drift region transit time introduces an additional delay Negative resistance characteristic is observed
22
IMPATT Ossilator
http://www.ecn.purdue.edu/WBG/Device_Research/IMPATT_Diodes/ 23
Critical Field
24
Drift Velocity
25
Ionization rates The number of electron-hole pairs generated by an electron/hole per unit distance traveled.
26
Limitations High noise oscillation frequency
Limitations of semiconductor materials
Critical field, at which avalanche breakdown occurs.
Vmax = EcW
Saturation velocity which is the maximum attainable velocity in semiconductors 27
Noise - Microwave Devices
IMPATT
BARITT
TED GaAs
TED InP
TUNNEL
MESFET
Bipolar
Noise Figure in dB
35.0 30.0 25.0 20.0 15.0 10.0 5.0 0.0
Devices
28
Applications Single Diode Waveguide Switch Traditional electronic sources of THz light Receivers Source of CW Electromagnetic vawe
29
Applications • Laser diode transmitters on Port Cards inside detector Total 570 transmitters 128 Port Cards, • PIN diode receivers on FTM board out in VME crates
30
References Physics of semiconductor Devices, S. M. Sze, Bell Lab www.ctr.kcl.ac.uk/lectures/Johnk www.bock-bock.cisco.com www.ecn.purdue.edu Microwave devices, quantum effect, and hot-electron devices, Catlech Watson Lab presentation
31
Marjan Alavi School of Electrical Engineering Sharif University of Technology
1
Outline Intoduction APD PIN Diodes IIMPATT Devices Applications References
2
Photodiode Basic Principle
O-E Converter The Electron-Hole Pair Give Rise to an Electrical Current Conduction Band
Electron
ΔE
Absorption
E=hc/λ Photon
Hole
Valence Band
bock-bock.cisco.com/~abarbier 3
Photodetectors P-I-N photodiodes: Intrinsic
layer of semiconductor between the p-doped and n-doped side to extend the usable area to receive photons
Avalanche Photo Diode (APD): strongly
biased (reverse biasing) pn diode that creates many electron-hole pairs per each photon received; Aplifies the signal :improved sensitivity
http://hepunx.rl.ac.uk/BFROOT/
4
General Principles The photogenerated current, Iph, increases linearly with: The
optical power Magnitude Ratio of Iph to the incident optical power, Φ: responsivity, ℜ of the photodiode.
The
5
The Ideal Photodiode All the incident light would be absorbed The quantum efficiency would then be unity Minimizing reflection at the incident surface; Maximizing the absorption within the depletion layer Avoiding recombination before the carriers are collected. 6
Basic Photodiode Configuration Good
linearity Low noise High frequency response Easy to manufacture
7
PIN Photodiode Absorptive p InP
i
n
InGaAs
InP
Optical Input
Transparent
VR bock-bock.cisco.com/~abarbier
8
Response Time CR time constant of the diode capacitance and its load Carrier transit time within the diode local recombination time Bandwidths exceeding 1GHz are practical. 9
Quantum Efficiency Quantum efficiency, η, for a given device:
the ratio between Iph, measured in electrons per second and the incident optical flux, measured in photons per second. η = Iph/e ÷ Φ/εph = (Iph/Φ).(hc/eλ) = ℜ. (hc/eλ)
10
Bandwidth Bandwidth = 1/ ttr
11
Noise
12
Singal to Noise Ratio
13
PIN Sample P+ layer: 103nm (1/4 l ) I-layer: 2µm 11(1/2 l), h=0.99 N- layer: 2µm 22(1/4 l) Responsivity: 1.04A/W Response time: 28.6 psec Minimum detectable signal: 250W/cm2 14
APD principle of operation Incident photons generate charge carriers in the depletion region Accelerated to high speeds by an applied electric field Ionize atoms within the avalanche region
http://optics.org/articles
15
APD Application High sensitivity at high-speed operation: optical
communications
http://optics.org/articles 16
APD optimum operating
point Detector's signalto-noise ratio is APDs are the preferred choice if:
light levels are limited (microwatts or nanowatts) A fast response (up to gigahertz) is required.
http://optics.org/articles
17
IMPATT Diode Impact Avalanche And Transit Time diode Operates in reverse-breakdown (avalanche) region Applied voltage causes momentary breakdown once per cycle This starts a pulse of current moving through the device Utilizes impact ionization and transfer time delay to generate negative resistance
Frequency depends on device
18
IMPATT Structure High density next to the junction reduce E from 300500 for avalanche to 15 KV/cm for Vsat in drift region P+ n n+ or P+ nin+
19
Static Characteristics High Electric field (E=3 – 6 e5 V/cm) Avalanche multiplication Generating E/H pairs Drift velocity Negative resistance
20
Satic Characteristics
with proper choice of doping and region width, avalanche region can be entirely contained within region with doping N1 21
Dynamic Characteristics Avalanche region introduces phase shift of π /2 in the injected carrier density For π<ωt<2π, carriers drift across to n+-contact Carriers will drift at saturation velocity Drift region transit time introduces an additional delay Negative resistance characteristic is observed
22
IMPATT Ossilator
http://www.ecn.purdue.edu/WBG/Device_Research/IMPATT_Diodes/ 23
Critical Field
24
Drift Velocity
25
Ionization rates The number of electron-hole pairs generated by an electron/hole per unit distance traveled.
26
Limitations High noise oscillation frequency
Limitations of semiconductor materials
Critical field, at which avalanche breakdown occurs.
Vmax = EcW
Saturation velocity which is the maximum attainable velocity in semiconductors 27
Noise - Microwave Devices
IMPATT
BARITT
TED GaAs
TED InP
TUNNEL
MESFET
Bipolar
Noise Figure in dB
35.0 30.0 25.0 20.0 15.0 10.0 5.0 0.0
Devices
28
Applications Single Diode Waveguide Switch Traditional electronic sources of THz light Receivers Source of CW Electromagnetic vawe
29
Applications • Laser diode transmitters on Port Cards inside detector Total 570 transmitters 128 Port Cards, • PIN diode receivers on FTM board out in VME crates
30
References Physics of semiconductor Devices, S. M. Sze, Bell Lab www.ctr.kcl.ac.uk/lectures/Johnk www.bock-bock.cisco.com www.ecn.purdue.edu Microwave devices, quantum effect, and hot-electron devices, Catlech Watson Lab presentation
31
