MBE grown ZnCdMgSe materials for near to mid IR …...1 MBE grown ZnCdMgSe materials for near to mid IR wavelength intersubband devices Joel De Jesus, Thor A. Garcia, Goupeng Chen,

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MBE grown ZnCdMgSe materials for near to mid IR wavelength

intersubband devices Joel De Jesus, Thor A. Garcia, Goupeng Chen, Vasilios Deligianakis, Arvind Ravikumar, Claire Gmachl, Aidong Shen, Maria C. Tamargo

Quantum Well

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Barrier Barrier QW

The building block of all the intersubband devices is the Quantum Well (QW). To make a Quantum Well, a low bandgap semiconductor is sandwiched between a higher bandgap semiconductor

Intersubband transitions

3

H1

CB E2

E1

H2 ΔEv

VB

Band to band

Intersubband

Confinement in a quantum well (QW) splits the bands into discreet levels. Intersubband transitions happen within the energy levels from the same band

Intersubband devices

QC Laser Quantum well infrared photodetector (QWIP) Quantum Cascade

(QC) Detector

Environment Industry Medicine Military

DETECTORS EMMITERS

Quantum wells are the building blocks to make Intersubband devices

Commercial QC Lasers wavelength limits

The shortest IR wavelength commercial QCL available today operates at 3.42 µm. A small conduction band offset and intervalley scattering limit the most mature material system from reaching shorter wavelengths.

Efficiency drops below 4.0 µm

I will present here the use of a family of II-VI selenides that have properties that will enable the expansion of these devices to shorter than 3.4 µm wavelengths.

Why shorter IR wavelengths?

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Application #1: Trace gas sensing, LIDAR

Atmospheric window between 2 - 2.7um

NH3

NO V.A. Saptari Thesis (Ph. D.) - Massachusetts Institute of Technology, Dept. of Mechanical Engineering

Applications #2: non-invasive glucose detection

Liquid water has low absorption window between 2.1 - 2.3 µm

Glucose has distinctive absorptions in that window

Molecular Beam Epitaxy (MBE)

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Effusion cell

Shutter motor

Liquid N2

Substrate rotation

RHEED screen

Photograph of the II-VI MBE chamber at CCNY

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Effusion cell

MBE enables layer by layer growth of materials with enough precission to make quantum well based devices

Molecular Beam Epitaxy (MBE)

8

Effusion cell

Shutter motor

Liquid N2

Substrate rotation

RHEED screen

Photograph of the II-VI MBE chamber at CCNY

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Effusion cell

MBE enables layer by layer growth of materials with enough precission to make quantum well based devices

ZnCdMgSe Lattice matched to InP

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• Widely tunable band gap (2.1 to 3.6 eV when lattice-matched to InP)

• 80% of band discontinuity is in conduction band structures with widely tunable CBO (0 eV to 1.1 eV when lattice-matched to InP)

ZnxCdyMg(1-x-y)Se

M. Munoz et al Appl. Phys. Lett. 83, 1995 (2003).

CBO ~ 0.8ΔEg

For Lattice Matched Materials CBO ~ 0.8 (EgBARRIER– 2.1 eV) CBOMAX ~ 1.12 eV

Our materials properties

No intervalley scattering

Growing lattice matched materials is like playing LEGGO


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ZnxCdyMg(1-x-y)Se


CBO ~ 0.8ΔEg



No intervalley scattering ZnCdSe


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ZnxCdyMg(1-x-y)Se


CBO ~ 0.8ΔEg





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ZnxCdyMg(1-x-y)Se


CBO ~ 0.8ΔEg





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ZnxCdyMg(1-x-y)Se


CBO ~ 0.8ΔEg




State of the art II-VI of QC Emitters

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Long Wavelength 6.6 µm design (A3432 EL). Emits at 7.0 µm

500 1000 1500 2000 2500 30000

5

10

15

20

25

30

Wavenumbers (cm-1)

Inte

nsity

(a.u

.) 2.0 A 1.8 A 1.6 A

80 K, 80 kHz, 200 ns

500 1000 1500 2000 2500 30000

5

10

15

20

1 A

80 K 100 K 120 K 140 K 160 K 180 K 200 K 220 K 260 K 280 K

Inte

nsity

(a.u

)

Wavenumbers (cm-1)

80 kHz, 200ns1.6 A

M1_A3432_bottom

EL spectrum at High Currents Temperature dependent EL

Lorentzian peak observed

until 160 K. EL peak at 7 µm

still observed at 280 K.

59 60 61 62 63 64 65 66 67 68

B

A

BA3432 004

Small mismatch in the structure. Sharp

superlattice peaks.

XRD around InP (004)

1st Example of devices made with lattice matched materials

State of the art II-VI QC Detectors

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0 10 20 30 40

0.0

0.2

0.4

0.6

0.8

6

1'

34

2

5

Ener

gy (e

V)

Position (nm)

300 K

1

1000 2000 3000 4000 50000.00

0.02

0.04

0.06

0.08

0.10

0.12

InP

epilayer

signal

IR source

E5/4 E2/1

120 K 100 K 80 K

Resp

onsiv

ity (m

A/W

)

Wavenumber (cm-1)

E3 E1

E21 = 340 meVE45 = 456 meVE41 = 501 meV

108 6 4 2Wavelength (µm)

II-VI Quantum Cascade Detector

310 µm

485

µm

• QC Detectors are IR photodetectors that operate at zero bias owing to an asymmetric quantum design.

• Demonstration of the first II-VI ZnCdSe/ZnCdMgSe based photovoltaic QC Detector operating in the short-IR wavelength 2 – 5 μm regime.

• Low noise at room temperature, and high detectivity achieved.

Temperature dependent photocurrent spectrum of the QCD indicating short-

wavelength operation. (inset) Schematic of the device used in measurements.

QC detectors devices made at Princeton

A portion of the conduction band of the short-wave II-VI QCD with the relevant energy level noted. 15

25 26 27 28 29 30 31 32 33 34 35 36

Inte

nsity

(arb

. uni

ts)

2Theta (deg)

A3303 HR-XRD (002)

XRD around InP (002)

2nd Example of devices made with lattice matched materials

Strain engineering to enhance ISB devices

Lattice matched ZnCdMgSe system

ZnCdSe

ZnCdMgSe

CBOMAX ~ 1.12 eV

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Shorter wavelengths: Increasing the CBO.

Use the binary CdSe as the quantum well (QW) material.

ZnCdSe

ZnCdMgSe

CBOMAX ~ 1.12 eV CBOMAX

~ 1.44 eV

CdSe

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ZnSe layers will strain balance CdSe layers

ZnCdSe

ZnCdMgSe


~ 1.44 eV

CdSe

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Lattice mismatch of ZnSe and CdSe (ZnSe-InP)/(ZnSe) = -0.019/0.586 = -0.0343 (CdSe-InP)/(CdSe) = 0.021/0.586 = 0.0354


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Sample tZnSe tCdSe tCdSe/tZnSe Δa/a

A 20/20 s 52 s 1.3 -0.53%

B 8/8 s 40 s 2.5 -0.41%

C 6/6 s 32 s 2.6 -0.23 %



ZnSe layers will strain balance CdSe layers

ZnCdSe

ZnCdMgSe


~ 1.44 eV

CdSe

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Results and discussion

A3414 A3456 A3300

XRD (004)

RT PL

FTIR Abs

500 550 600 650 700 750 800

Inte

nsity

(Arb

. uni

ts)

wavelength (nm)

1.95 eV

500 550 600 650 700 750 800

Cou

nts

Wavelength (nm)

1.86 eV

500 550 600 650 700 750 800

Inte

nsity

(Arb

. uni

ts)

wavelength (nm)

1.80 eV

56 58 60 62 64 66 68

Inte

nsity

(Arb

. Uni

ts)

2 theta56 58 60 62 64 66 68

Cou

2 Theta

2700 3000 3300 3600 3900

Energy (cm-1)

3.04 µm

2700 3000 3300 3600 3900

H

A

2.65 µm

56 58 60 62 64 66 68

Cou

nts

2 theta

B

Excellent material quality and optical properties Achieved short wavelength with only a 2.85 eV barrier energy Can extend wavelength by using higher bandgap barrier or improving QW design

Sample tCdSe RT PL FTIR Absorption

A (A3300)

52 s 1.80 eV 3.44 µm

B (A3414)

40 s 1.86 eV 3.04 µm

C (A3456)

32 s 1.95 eV 2.65 µm

All PL emissions below the bandgap of the lattice matched ZnCdSe (2.1 eV) demonstrates the achievement of deeper quantum wells.

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2700 3000 3300 3600 3900

Arb.

Uni

ts

Energy (cm-1)

3.44 µm

Conclusions

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• Demosntrated good electroluminescence properties from lattice matched ZnCdMgSe materials. Lasing is still elusive.

• Demonstrated good performance lattice matched ZnCdMgSe QC detectors for wavelengths as short as 2.3 µm

• Demostrated that lattice matched ZnCdMgSe systems are robust and ready for the commercialization of short to mid IR devices

• Extended the use of this material system to non-lattice matched alloys for shorter wavelengths

Future Work

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Lattice Matched ZnCdMgSe alloys

Configurations to be considered to create a two asymmetric coupled quantum well system to be used as a short wavelength QC laser active region.

MIRTHE SLIP Grant – Broadband QC Detectors

Strain compensated ZnCdMgSe alloys

Special Thanks

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Professor Maria C. Tamargo

Professor Aidong Shen

Luis Hernández Zhiyi Chen Vasilios Deligiannakis Siddharth Dhomkar

Thor Garcia Kuaile Zhao

Professor Claire Gmachl Arvind Ravikumar

Design, Processing and characterization of II-VI Devices

Guopeng Chen

Part of the collaborative

team

Documents

MBE grown ZnCdMgSe materials for near to mid IR …...1 MBE grown ZnCdMgSe materials for near to mid IR wavelength intersubband devices Joel De Jesus, Thor A. Garcia, Goupeng Chen,