About APSYSAPSYS, Advanced Physical Models of Semiconductor Devices,

is based on 2D/3D finite element analysis of electrical, optical

and thermal properties of compound and silicon semiconductor

devices. Emphasis has been placed on band structure

engineering and quantum mechanical effects. Inclusion of various

optical modules also makes this simulation package attractive for

applications involving photosensitive or light emitting devices.

Models and FeaturesAPSYS is a full 2D/3D simulator, which solves, self-consistently,

the Poisson’s equation, the current continuity equations, the carrier

energy transport equations (hydrodynamic model), quantum

mechanical wave equations, and the scalar wave equations for

photonic waveguiding devices. Applicable features for modeling

photo-detectors and avalanche photodiodes include the following

features.

Physical Models &Advanced Features

Hydrodynamic models for hot carriersQuantum wells and k.p theoryThermionic emission modelImpact ionization modelsIntersubband optic absorptionField dependent mobility modelDoping density dependent lifetimeInterface states and recombinationTemperature dependent model and lowtemp(<77K) simulationA large number of material models

Application DemonstrationsPhotodetectors have extensive applications in fields from

astronomical observation, remote sensing imagers and optic fiber

communications etc. Modeling capabilities are here demonstrated

with PIN photo-diodes, separate absorption, grading, charge, and

multiplication avalanche photo-diodes (SAGCM APDs) for optic

fiber communications, and quantum well infrared photodiodes

(QWIPs) for remote sensing.

p-layer i-layer i-layer n-layerEnergy buildup layer Multiplication layer

Al0.6Ga0.4As GaAs

hv

Intrinsic Al0.6Ga0.4Aslayer for energybuildup purpose

See: Kwon et al, J. LightwaveTechnol. Vol 23 No 5(2005) pp 1896-1906

p++ 30-nm GaAs

p+ 800-nm GaAs

n+ 300-nm GaAs

n+ GaAs Substrate

i 200-nm GaAs

i "x"-nm Al(.6)Ga(.4)As

(~1e19cm-3)

(5e18cm-3)

(5e18cm-3)Photocurrent(A/m)

Reverse Bias (V)0

0.01

0.1

1

2 4 6 8 10 12 14 16 18

0

0

1

-1

2

0.2-1.5

0.5

0.5

1.5

0.4 0.6 0.8 1 1.2 1.4 1.6Distance (micron)

Energy(eV)

With hotelectron effect

Withouthot electr. effect

Modeling results for InP/InGaAs SAGCM APDS are presented

below. The basic InP/InGaAs SAGCM device structure can be

built up with Crosslight Layer Builder.

Advanced Simulation of Photodetectors

using APSYS

Optical absorption is mainly in InGaAs layer and impact ionization

mainly in n- InP layer.

For QWIPs, the single well bound and unbound states from

APSYS modeling is presented below.

For full QWIP device, the modeling results show good agreement

with experiment.