# Presentation: 033262

## 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**

## 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

## Breakdown Probabilities

- Pbe=1-Pnbe and Pbh=1-Pnbh
- where Pbe(h) = probability of electron (hole) initiated breakdown
- 	Pnbe(h) = probability breakdown does not occor

## Breakdown Probability for GaAs PIN 

**Case 1: Pure hole injection**

**Case 2: Pure electron injection**

## Breakdown Probability: Function of Multiplication Layer Thickness

## Monte Carlo Calculated Gain Distributions

- Fewer “outliers” in short devices

**Monte Carlo Calculated Gain Distributions**

## Breakdown Probability: Function of Material System

## Breakdown Probability Results to Date

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

## Experimental Results

## Photon Counting Apparatus

## Spectrolabs In0.52Al0.48As/In0.53Ga0.47As APD

**Multiplication**

**Absorber**

***i***

**: **

**InGaAs**

**, 1000nm**

***p***

**: **

**InAlAs**

**, , **

**3**

****

**10**

**17,**

**200nm**

***i***

**: **

**InAlAs**

**, 400nm**

***n+***

**: **

**InAlAs**

**, **

**5**

****

**10**

**18**

**, 100nm**

***n+***

**: InP**

**, **

**5**

****

**10**

**18**

**, 500nm**

***Semi***

***-***

***insulating***

**: InP Substrate**

***i***

**: **

**InAlAs **

**Transition, 50nm**

***i***

**: **

**InAlAs **

**Spacer, 50nm**

***i***

**: **

**InAlAs **

**Transition, 50nm**

**Multiplication **

**Absorber**

***i***

**: **

**InGaAs**

**, 1000nm**

***p***

**: **

**InAlAs**

**, , **

**3**

****

**10**

**17,**

**200nm**

***i***

**: **

**InAlAs**

**, 400nm**

***n+***

**: **

**InAlAs**

**, **

**5**

****

**10**

**18**

**, 100nm**

***n+***

**: InP**

**, **

**5**

****

**10**

**18**

**, 500nm**

***Semi***

***-***

***insulating***

**: InP Substrate**

***i***

**: **

**InGaAlAs **

**Transition, 50nm**

***i***

**: **

**InAlAs **

**Spacer, 50nm**

***i***

**: **

**InGaAlAs **

**Transition, 50nm**

**Multiplication **

**Absorber**

***p***

**+: **

**InGaAs**

**9**

****

**10**

**18, **

**50nm**

***p***

**+: **

**InAlAs**

**5**

****

**10**

**18**

**, 300nm**

***i***

**: **

**InGaAs**

**, 1000nm**

***p***

**: **

**InAlAs**

**, , **

**3**

****

**10**

**17,**

**200nm**

***i***

**: **

**InAlAs**

**, 400nm**

***n+***

**: **

**InAlAs**

**, **

**5**

****

**10**

**18**

**, 100nm**

***n+***

**: InP**

**, **

**5**

****

**10**

**18**

**, 500nm**

***Semi***

***-***

***insulating***

**: InP Substrate**

***i***

**: **

**InAlAs **

**Transition, 50nm**

***i***

**: **

**InAlAs **

**Spacer, 50nm**

***i***

**: **

**InAlAs **

**Transition, 50nm**

***p***

**+: **

**InGaAs**

**9**

****

**10**

**18, **

**50nm**

***p***

**+: **

**InAlAs**

**5**

****

**10**

**18**

**, 300nm**

** **

***i*****: InGaAs**

**, 1000nm**

***p***

**: **

**InAlAs**

**, , **

**3**

****

**10**

**17,**

**200nm**

***i***

**: **

**InAlAs**

**, 400nm**

***n+***

**: **

**InAlAs**

**, **

**5**

****

**10**

**18**

**, 100nm**

***n+***

**: InP**

**, **

**5**

****

**10**

**18**

**, 500nm**

**N+: InP Substrate**

***i***

**: **

**InGaAlAs **

**Transition, 50nm**

***i***

**: **

**InAlAs **

**Spacer, 50nm**

***i***

**: **

**InGaAlAs **

**Transition, 50nm**

**Multiplication**
** ****region**

**Absorber**

## Photon Counting: Device Comparison

## Designing a Better Single Photon Counting APD

## Simplified structures for calculation

***Undepleted SACM structure***

***ordinary SACM***

**Simplified structures for calculation**

## Comparison: Electric Field Profile

**Comparison: Electric Field Profile**

## Comparison:Breakdown Probability

**Comparison:Breakdown Probability**

- More localized electric field leads to sharper
- increase in PBR above breakdown

## APD with Undepleted Absorber

**Field in the absorber **
**due to doping gradient**

## APD with Undepleted Absorber: Photo response

## APD with Undepleted Absorber: Gain and F(M)

**Bias (V)**

**8**

**10**

**12**

**14**

**16**

**18**

**Gain**

**2**

**4**

**6**

**8**

**10**

**12**

**14**

**16**

**18**

**20**

**22**

**24**

**Measured**

**Simulated**

**C=2.212m**

**Multiplication**

**5**

**10**

**15**

**20**

**25**

**30**

**35**

**40**

**F(M)**

**0**

**2**

**4**

**6**

**8**

**10**

**12**

**F(M) for different k**

**Simulated**

**Measured**

**k=0.2**

**k=0.1**

**k=0**

**k=0.3**

**k=0.15**

## APD with Undepleted Absorber: Gain-Bandwidth

**Gain (M)**

**1**

**10**

**100**

**Bandwidth (GHz)**

**1**

**10**

**GB= 160 GHz**

**APD with Undepleted Absorber: Gain-Bandwidth**