Porous Si LEDs

1
Photon-Counting Avalanche Photodiodes  
Gauri Karve, Shuling Wang, Feng Ma, Xiaoguang
Zheng, Ning Li, Rubin Shidu, Joe Campbell, and
Archie Holmes, Jr.
Microelectronics Research Center Department of
Electrical and Computer Engineering The
University of Texas at Austin
2
Theoretical Design Goals

• Develop both analytical and Monte Carlo models to
  predict important parameters for single photon
  counting
• Dark current as a function of temperature
• Breakdown probabilities
• Dark Count Probability
• Determine what materials/structure is best for
  the multiplication region of a single photon
  counting APD

3
Breakdown Probabilities
Pbe1-Pnbe and Pbh1-Pnbh where Pbe(h)
probability of electron (hole) initiated
breakdown Pnbe(h) probability breakdown does
not occor
4
Breakdown Probability for GaAs PIN
Case 2 Pure electron injection
Case 1 Pure hole injection
5
Breakdown Probability Function of
Multiplication Layer Thickness
6
Monte Carlo Calculated Gain Distributions
Significant contribution to F(M) from the tail of
the distribution Fewer outliers in short
devices
7
Breakdown Probability Function of Material System
8
Breakdown Probability Results to Date

• Thicker multiplication regions lead to higher
  breakdown probabilities for the same DVBR/VBR
  ratio
• PBR trends follow those expected from bulk
  ionization coefficients
• Can you engineer the multiplication region to
  give a better PBR curve?

9
Experimental Results
10
Photon Counting Apparatus
11
Spectrolabs In0.52Al0.48As/In0.53Ga0.47As APD



InGaAs
9
10
18,
50nm

InGaAs
9
10
18,
50nm
p
p


18
18
p

InAlAs
5
10
, 300nm
p

InAlAs
5
10
, 300nm

InAlAs
Transition, 50nm

InGaAlAs
Transition, 50nm

InAlAs
Transition, 50nm

InGaAlAs
Transition, 50nm
i
i
i
i

i InGaAs
, 1000nm
Absorber
Absorber
Absorber
Absorber
i

InGaAs
, 1000nm
i

InGaAs
, 1000nm
i

InGaAs
, 1000nm

InAlAs
Transition, 50nm

InGaAlAs
Transition, 50nm

InAlAs
Transition, 50nm

InGaAlAs
Transition, 50nm
i
i
i
i

InAlAs
Spacer, 50nm

InAlAs
Spacer, 50nm

InAlAs
Spacer, 50nm

InAlAs
Spacer, 50nm
i
i
i
i





InAlAs
, ,
3
10
17,
200nm

InAlAs
, ,
3
10
17,
200nm

InAlAs
, ,
3
10
17,
200nm

InAlAs
, ,
3
10
17,
200nm
p
p
p
p
i

InAlAs
, 400nm
i

InAlAs
, 400nm
i

InAlAs
, 400nm
i

InAlAs
, 400nm
Multiplication
Multiplication
Multiplication
Multiplication region




18
18
18
18
n

InAlAs
,
5
10
, 100nm
n

InAlAs
,
5
10
, 100nm
n

InAlAs
,
5
10
, 100nm
n

InAlAs
,
5
10
, 100nm




InP
,
5
10
18
, 500nm
InP
,
5
10
18
, 500nm
InP
,
5
10
18
, 500nm
InP
,
5
10
18
, 500nm
n
n
n
n
Semi
-
insulating
InP Substrate
Semi
-
insulating
InP Substrate
Semi
-
insulating
InP Substrate
N InP Substrate
12
Photon Counting Device Comparison
13
Designing a Better Single Photon Counting APD
14
Simplified structures for calculation

ordinary SACM
Undepleted SACM structure
15
Comparison Electric Field Profile
A more localized field distribution in USACM
16
ComparisonBreakdown Probability
More localized electric field leads to
sharper increase in PBR above breakdown
17
APD with Undepleted Absorber
Field in the absorber due to doping gradient
18
APD with Undepleted Absorber Photo response
19
APD with Undepleted Absorber Gain and F(M)
24
k0.3
F(M) for different k
12
22
Simulated
Measured
20
Measured
Simulated
10
18
k0.2
16
8
k0.15
14
Gain
F(M)
12
6
k0.1
C2.212m
10
4
8
6
2
k0
4
2
0
5
10
15
20
25
30
35
40
8
10
12
14
16
18
Multiplication
Bias (V)
20
APD with Undepleted Absorber Gain-Bandwidth
GB 160 GHz
10
Bandwidth (GHz)
1
1
10
100
Gain (M)