1. InP/InGaAsP/InGaAs SWIR APDs
Separate absorption, grading, charge, and multiplication (SAGCM) structure
Carrier collection in absorber: low but finite field in absorber (avoid tunneling)
Multiplication gain: high field for impact ionization i - n +
InP buffer
InGaAsP grading
InP charge
InP cap
SiNx passivation
p-contact metallization
InP substrate
n-contact metallization
optical input E
InGaAs absorption
multiplication region
p+-InP diffused region
anti-reflection coating
Al0.6InAsSb
multiplication
Long-wavelength
absorber

2. External Quantum Efficiency
60%
30%
50%
40%
70%

3. External Quantum Efficiency
60%
30%
50%
40%
70%

4. AlInAsSb SACM APD p-type contact blocking layer graded bandgap
p+:GaSb 11019, 30 nm
p+: AlxIn1-xAlyAs1-y x = 0.7 to 0.4, 100 nm
p+: Al0.7In0.3As0.3Sb0.7 21018, 100 nm
n+: GaSb, 11018, buffer
n+:GaSb Substrate
n-: Al0.4In0.6As0.3Sb0.7, 1,000 nm
p+: AlxIn1-xAlyAs1-y x = 0.4 to 0.7, 100 nm
p: Al0.7In0.3As0.3Sb 1017, 150 nm
n-: Al0.7In0.3As0.3Sb0.7, 1,000 nm
absorption layer
multiplication layer
n-type contact
charge layer
p-type contact
graded bandgap
blocking layer
Electric field

5. AlInAsSb SACM Current-Voltage Characteristics
10-9
10-8
10-7
10-6
10-5
10-4
10-3
Gain
Photocurrent
Dark current

6. Noise Measurement of AlInAsSbk=
0.07 ↑
Measured with a 100 µm device.
k= 0.05 from fitting, punch-through.

7. APD Comparison 100 Gb/s Ethernet 400 Gb/s Ethernet 2q(iph+idark)M2F(M)