PVMD Ren van Swaaij Delft University of Technology Learning - - PowerPoint PPT Presentation

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PVMD Ren van Swaaij Delft University of Technology Learning - - PowerPoint PPT Presentation

Nov 28, 2023 269 likes •914 views

Heterojunctions PVMD Ren van Swaaij Delft University of Technology Learning objectives Why use a heterojunction? 2 Learning objectives Why use a heterojunction? Types of heterojunctions 3 Learning objectives Why use a

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PVMD

Delft University of Technology

Heterojunctions

René van Swaaij

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2

Learning objectives

  • Why use a heterojunction?
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3

Learning objectives

  • Why use a heterojunction?
  • Types of heterojunctions
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4

Learning objectives

  • Why use a heterojunction?
  • Types of heterojunctions
  • Construct a band diagram of a heterojunction
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Why go for a heterojunction?

Open circuit voltage

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Why go for a heterojunction?

Open circuit voltage

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Why go for a heterojunction?

Open circuit voltage 𝑊

  • c = 𝑙𝑈

𝑟 ln 𝐾ph 𝐾0 + 1 Saturation current density

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Why go for a heterojunction?

Open circuit voltage 𝑊

  • c = 𝑙𝑈

𝑟 ln 𝐾ph 𝐾0 + 1 Saturation current density

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9

Why go for a heterojunction?

Open circuit voltage 𝑊

  • c = 𝑙𝑈

𝑟 ln 𝐾ph 𝐾0 + 1 Saturation current density

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Why go for a heterojunction?

Open circuit voltage 𝑊

  • c = 𝑙𝑈

𝑟 ln 𝐾ph 𝐾0 + 1 is a material property Saturation current density

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Electron affinity

EF Evac

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Electron affinity

EF Evac qχsem

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Electron affinity

EF Evac qχsem qφsem

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Electron affinity

Evac EF

Semiconductor Electron affinity (V) Ge 4.13 Si 4.01 GaAs 4.07 AlAs 3.50

qχsem qφsem

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Bandgap alignment: Straddling

EV2 EC2 EC1 EV1 qχ2 Evac qχ1

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Bandgap alignment: Staggered

EV2 EC2 EC1 EV1 Evac qχ2 qχ1

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Bandgap alignment: Broken gap

EC1 EV2 EC2 EV1 Evac qχ2 qχ1

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Bandgap alignment

EV1 EC1 EV2 EC2

Broken gap

EV2 EC2 EC1 EV1 EV2 EC2 EC1 EV1

Staggered Straddling

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Bandgap alignment

EV1 EC1 EV2 EC2

Broken gap

EV2 EC2 EC1 EV1 EV2 EC2 EC1 EV1

Staggered Straddling

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Band diagram

ECn ECn EVP ECP

n type P type

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Band diagram

ECn ECn Egn EVP ECP

n type P type

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Band diagram

ECn ECn Egn EVP ECP EgP

n type P type

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Band diagram

ECn ECn EFn EVP ECP EFP

n type P type

Egn EgP

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Band diagram

Evac ECn ECn EFn qφsn qχn EVP ECP EFP Egn EgP qφsP qχP

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Band diagram

ECn ECn EFn EVP ECP EFP ΔEC ΔEV Egn EgP qφsn qχn qφsP qχP Evac

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Evac

Band diagram

ECn ECn EGn EFn EVP ECP EFP ΔEV qφsn EgP qφsP ΔEC qχn qχP

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Evac

Band diagram

ECn ECn EGn EFn EVP ECP EgP EFP ΔEV qφsn qφsP ΔEC qχn qχP

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Evac

Band diagram

ECn ECn EGn EFn EVP ECP EgP EFP ΔEV qφsn qφsP ΔEC qχn qχP

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Evac

Band diagram

ECn ECn EFn EVP ECP EFP qφsn qχn qφsP qχP Egn EgP ΔEC ΔEV

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Evac

Band diagram

ECn ECn EFn EVP ECP EFP qφsn qχn qφsP qχP ΔEC ΔEV Egn EgP

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Evac

Band diagram

ECn ECn EFn EVP ECP EFP qφsn qχn qφsP qχP ΔEC ΔEV Egn EgP

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Evac

Band diagram

ECn ECn EFn EVP ECP EFP qφsn qχn qφsP qχP ΔEC ΔEV Egn EgP

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Electron affinity rule

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Electron affinity rule

  • Assumption: also the case when interface is formed
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Electron affinity rule

  • Assumption: also the case when interface is formed
  • In reality: mixing of materials / lattice mismatch
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Band diagram

ECn ECn Egn EFn EVP ECP EgP EFP qφsn qχn qφsP qχP Evac

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Band diagram

EgP EVP ECP EFP EFn Egn EVn ECn Evac qφsn qχn qφsP qχP

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Band diagram

EFP EFn Evac x EVP ECP EVn ECn qφsn qχn qφsP qχP EgP Egn

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Band diagram

EFP EFn Evac x EVP ECP EVn ECn qφsn qχn qφsP qχP EgP Egn

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Band diagram

EFP EFn ΔEC ΔEV Evac x EVP ECP EVn ECn qφsn qχn qφsP qχP EgP Egn

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Band diagram

EFP EFn ΔEC ΔEV qVbiP qVbin Evac x EVP ECP EVn ECn qφsn qχn qφsP qχP EgP Egn

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Band diagram

EFP EFn ΔEC ΔEV qVbiP qVbiP qVbin qVbin Evac x EVP ECP EVn ECn qφsn qχn qφsP qχP EgP Egn

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Band diagram

EFP EFn ΔEC ΔEV qVbiP qVbiP qVbin qVbin qVbi Evac x EVP ECP EVn ECn qφsn qχn qφsP qχP EgP Egn

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EFP EFn ΔEC ΔEV qVbiP qVbiP qVbin qVbin Evac x EVP ECP EVn qχn EgP Egn ECn qχP qVbi

Band diagram

qφsn qφsP

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EFP EFn ΔEC ΔEV qVbiP qVbiP qVbin qVbin Evac x EgP Egn EVP ECP EVn qχn ECn qχP qVbi

Band diagram

qφsn qφsP

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EFP EFn ΔEC ΔEV qVbiP qVbiP qVbin qVbin Evac x EgP Egn EVP ECP EVn qχn ECn qχP qVbi

Band diagram

qφsn qφsP

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EFn ΔEC ΔEV qVbiP qVbiP qVbin qVbin qVbi Evac x Egn ECP EVn qφsn qχn ECn EvP EFP EgP

Band diagram

qφsP qχP

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EFn qsn qn ΔEC ΔEV qVbiP qVbiP qVbin qVbin qVbi Evac x Egn ECP EVn ECn EvP EFP EgP

Band diagram

qφsP qχP

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EFn qsn qn ΔEC ΔEV qVbiP qVbiP qVbin qVbin qVbi Evac x Egn ECP EVn ECn EvP EFP EgP

Band diagram

qφsP qχP

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EFn qsn qn ΔEC ΔEV qVbiP qVbiP qVbin qVbin qVbi Evac x Egn ECP EVn ECn EvP EFP EgP

Band diagram

qφsP qχP

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Electrostatic characteristics

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Electrostatic characteristics

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Electrostatic characteristics

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Band diagram

EFP EFn ΔEC ΔEV qVbiP qVbiP qVbin qVbin qVbi Evac x EVP ECP EVn ECn qφsn qχn qφsP qχP EgP Egn

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EFP EFn ΔEC ΔEV qVbiP qVbiP qVbin qVbin qVbi Evac x EVP ECP EVn ECn qφsn qχn qφsP qχP EgP Egn

Band diagram

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EFP EFn ΔEC ΔEV qVbiP qVbiP qVbin qVbin qVbi Evac x EVP ECP EVn ECn qφsn qχn qφsP qχP EgP Egn

Band diagram

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EFP EFn ΔEC ΔEV qVbiP qVbiP qVbin qVbin qVbi Evac x EVP ECP EVn ECn qφsn qχn qφsP qχP EgP Egn

Band diagram

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EFP EFn ΔEC ΔEV qVbiP qVbiP qVbin qVbin qVbi Evac x EVP ECP EVn ECn qφsn qχn qφsP qχP EgP Egn

Band diagram

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EFP EFn ΔEC ΔEV qVbiP qVbiP qVbin qVbin qVbi Evac x EVP ECP EVn ECn qφsn qχn qφsP qχP EgP Egn

Band diagram

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EFP EFn ΔEC ΔEV qVbiP qVbiP qVbin qVbin qVbi Evac x EVP ECP EVn ECn qφsn qχn qφsP qχP EgP Egn

Band diagram

Different transport characteristics

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Summary

  • Use heterojunction to change Voc
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Summary

  • Use heterojunction to change Voc
  • Discussed three types of band alignment
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Summary

  • Use heterojunction to change Voc
  • Discussed three types of band alignment
  • Constructed band diagram