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UV VIS OPTOELECTRONICS WITH OXIDES UV VIS OPTOELECTRONICS WITH OXIDES ADRIAN HIERRO, ELIAS MUOZ INSTITUTE OF SYSTEMS BASED ON OPTOELECTRONICS AND MICROTECHNOLOGY ELECTRONICS ENGINEERING DEPT. UNIVERSIDAD POLITECNICA DE MADRID (UPM), MADRID,

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SLIDE 1

UV VIS OPTOELECTRONICS WITH OXIDES

ADRIAN HIERRO, ELIAS MUÑOZ

UV‐VIS OPTOELECTRONICS WITH OXIDES

INSTITUTE OF SYSTEMS BASED ON OPTOELECTRONICS AND MICROTECHNOLOGY ELECTRONICS ENGINEERING DEPT. UNIVERSIDAD POLITECNICA DE MADRID (UPM), MADRID, SPAIN UNIVERSIDAD POLITECNICA DE MADRID (UPM), MADRID, SPAIN

  • A. Nakamura and J. Temmyo

Research Institute of Electronics Shizuoka University Hamamatsu Research Institute of Electronics, Shizuoka University, Hamamatsu JOINT JST‐MINECO PROJECT, SU‐UPM collaboration

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SLIDE 2

From “Wide bandgap semiconductors”, Springer 2007.

  • K. Takahashi, A. Yoshikawa, A. Sandhu, editors.

162 Committee JSPS

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SLIDE 3

ZnO

Why ZnCdMgO?

ZnO

 Easy to grow with with different plane orientations  High exciton binding energy 60 meV; Excitonic effects at RT  ZnO high quality substrates already available for homoepitaxy  A variety of nanostructures/shapes easily grown  Reactive surfaces and prone to get –OH groups  Reactive surfaces and prone to get –OH groups

ZnCdO → ZnO → Zn1‐xMgxO

 Potentially , bandgap control from (VIS)  2.2 eV to (UV)  8 eV  As an example, from present work, ZnMgO keep WZ structure up

to Mg 50% (4.4 eV) g ( )

DIFFICULTIES

‐to reach high Mg/Cd m fractions while keeping WZ S (NPS)

to reach high Mg/Cd m fractions while keeping WZ S (NPS)

‐to obtain reliable and robust p‐type doping

CAN ZnCdMgO NANOSTRUCTURES HELP TO

‐CAN ZnCdMgO NANOSTRUCTURES HELP TO

CIRCUNVENT SUCH PROBLEMS?

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SLIDE 4
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SLIDE 5
  • utline
  • RPE‐MOCVD growth reactor at SU
  • ZnCdO nanowires grown on a Sapphire paternned substrate:

search for high Cd content

  • Acceptors in undoped ZnMgO
  • Typical p‐doping results in ZnMgO layers

A t i N d d Z M O

  • Acceptors in N‐doped ZnMgO
  • MQW ZnCdO/p‐type SiC green LED

MQW nCdO/p type SiC green

  • Summary/reflections
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SLIDE 6

Zn(Mg,Cd)O:N by RPE‐MOCVD

Plasma spectrum in situ

RF13 56MH

Remote plasma Heater 10KHz

  • A. Nakamura, J. Temmyo, Shizuoka U.

OH

O2 plasma/ H2 carrier

Plasma spectrum in situ

RF13.56MHz

Oxygen/Hydrogen Nitrogen

O H y (arb. units) OH

substrate

MeCp2Mg (EtCp2Mg)

susceptor

O2 plasma/ N2 carrier

O2 N2 N2 N2 NO Intensity

DEZn DMCd H2/N2 MBP/RP Growth conditions: Pressure: 0.1Torr Temp: 300-600oC

200 300 400 500 600 700 800

Wavelength (nm)

Hi hl ilib i th

2 2

exhaust p

Highly non-equilibrium growth:

  • radical energy enhances decomposition and doping
  • WZ type ZnO alloys become available

6

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SLIDE 7

STRUCTURAL and OPTICAL PROPERTIES of ZnCdO NANOCOLUMNS

‐ PL+HRXRD*+microEDX+HRTEM* of ZnCdO nanocolumns

‐ Cd%: x=0, 0.14, 0.27 and 0.45!! ‐Length  1‐4 m SEM

*HRTEM/EDX collaboration with V.Muñoz, U.Valencia, SP

As‐grown RT

‐Length  1‐4 m ‐Diameter  100‐200 nm HRTEM

V.Muñoz, U.Valencia, SP

ZnO 14% Cd 27% Cd Annealed

y (a.u)

45% Cd

PL

PL Intensity

0.8 1.0 0.8 1.0

Con %) Zn Annealed nanowire

1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4

Energy (eV)

micro‐EDX

0.2 0.4 0.6 0.2 0.4 0.6

centration (at centration (at Cd

  • 1. Emission demonstrated down to 2.02 eV
  • 2. Only wurtzite phase observed even for

45% Cd, no phase separation!

0.0 0.1 0.2 0.3 0.4 0.5 0.0 0.1 0.2 0.0

Nanowire Surface

t %) Conc

Nanowire Tip Width (m) Lenght (m)

Results accepted for publication in Appl.Phys.Lett.

  • 3. State of the art ZnCdO nanocolumns!
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SLIDE 8

CHARACTERIZATION of ZnMgO (MOCVD) LAYERS (SU)

0.9 1.0

d <1120>

RBS determination of stoichiometry and quality*

10

17

m

  • 3)

5.6%Mg

DARK

C‐V profiles

0.7 0.8 0.9

alized yield

Nd-Na) (cm

9.5%Mg 14.5%Mg 18.0%Mg

0.5 0.6 Zn Mg O

Norma a-plane MgZnO

0 15 0 30 0 45 0 60 10

16

n=(N

  • 2.0
  • 1.5
  • 1.0
  • 0.5

0.0 0.5 1.0 1.5 2.0 0.4 O

Theta (º) MgZnO *Collaboration with A. Redondo, ITN, Portugal

0.15 0.30 0.45 0.60 Depth (m)

Zn1-xMgxO

1 O rich behavior of samples

DLOS + Lighted CV profiling

EC

Mg (%) n=(Nd-Na) (cm-3) Ev+280 meV (cm-3) Ev+580 meV (cm-3)

  • 1. O‐rich behavior of samples

2.Growth plane (a‐plane or c‐plane) does not affect Mg incorporation 3 ZnMgO is highly compensated

E

Ev+580 meV Ev+280 meV VZn (-/2-) * VZn (0/-) *

5.6 8.02x1016 1.08x1017 1.66x1016 9.5 1.98x1016 3.44x1017 1.54x1016 14.5 1.47x1016 8.62x1017 2.27x1016 18 0 1 27 1016 1 01 1018 5 23 1016

  • 3. ZnMgO is highly compensated

due to two acceptor levels related to VZn

  • 4. Can use ZnMgO samples to

EV

* A.F. Kohan et al. Phys.Rev.B 61, 15019 (2000)

18.0 1.27x1016 1.01x1018 5.23x1016

  • 4. Can use ZnMgO samples to

achieve p‐type doping

Same VZn related acceptors also found in MBE ZnMgO layers from JM Chauveau, CNRS‐CRHEA, FR

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SLIDE 9

Typical p‐doping results

  • A. Nakamura, J. Temmyo, Shizuoka U.

n-type p-type

MgZnO:(N,In,Cu) co-doping

n-type p-type

g ( , , ) p g showed p-type

  • N solubility enhanced by codoping

(N) acceptor activated

  • (N)O acceptor activated

against expectation:

  • n-type conductivity for N, Cu

n type conductivity for N, Cu

  • Conductivity-type change for N, In

was occurred under RTA activation. ref: morphology change after RTA

200nm 200nm

As grown RTA 800oC

9

  • S. Mohanta, et al. J. Appl. Phys 110 (2011) 013524.
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SLIDE 10

*Implanted profile (SRIM) Crystal recovery (RBS)

N‐implantation in MOCVD ZnMgO LAYERS

Optical emission (PL)

3000 3500 4000 As implanted +500 ºC (10')

s)

RBS/C 2 MeV He

+

=140º, Q=5 C 0.30 0.35 0.40

  • n Å

150 keV N 10º

Implanted profile (SRIM) Crystal recovery (RBS)

.)

MgxZn1-

xO (as grown)

(b)

x=15% x=9%

Optical emission (PL)

1500 2000 2500 +500 C (10 ) +700 ºC (10') +900 ºC (10') Random

Yield (counts

O Zn

0 10 0.15 0.20 0.25 Zn+O O

Vacancies / io

Zn

nsity (a.u

x=5% x=0%

400 600 800 1000 1200 1400 1600 500 1000

Y

Al

100 200 300 400 500 0.00 0.05 0.10

Depth (nm) V (b)

PL inten (c)

MgxZn1-xO:N (+RTA 900ºC)

Energy (keV)

Depth (nm)

*Collaboration with A. Redondo, ITN, Portugal CV profiling using Schottky diodes

3.3 3.4 3.5 3.6

Photon energy (eV)

1E18

5 % Mg 9 % Mg Implanted + RTA

m

  • 3)

As implanted

p f g g y

  • 1. N implantation at 150 keV

1E17

Implanted + RTA

Nd-Na (cm

  • 2. Implanted films are highly n‐type
  • 3. Best crystal recovery found at 900°C (strong Al
  • ut‐diffusion from substrate at higher T).

h l l d l d f l

0.138 0.207 0.276 0.345 1E16

as-grown

W (m)

1 KHz

  • 4. Thermal annealing reduces Xtal damage, films are

less n‐type, BUT no direct observation of p‐type behavior ; defects overcome N‐related acceptors

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SLIDE 11

MQW ZnCdO/ZnO/p‐SiC VIS LED

  • b. unit)

room temprerature

Mesa: 200m

FWHM: 690 meV

Layers grown at Shizuoka U. 5 QW ZnCdO (20% Cd) ensity (arb

80mA 70 A

Mesa: 200m

EL inte

70mA 60mA 40mA 20mA

1.5 2.0 2.5 3.0 3.5

Photon energy (eV)

10

  • 2

10

  • 1

Rectify ratio: 107 @4V unit)

  • 1. RT CW Emission at

2 55 V ( i h

5

10

  • 4

10

  • 3

10

2

ity (A/cm

2)

nsity, L (arb.

2.55eV (agreement with PL from ZnCdO/ZnO QW)

10

  • 7

10

  • 6

10

  • 5

urrent dens

grated EL inte

  • 2. First demonstration
  • f ZnCdO MQW LED

in literature!!....green

  • 4
  • 3
  • 2
  • 1

1 2 3 4 10

  • 9

10

  • 8

C Voltage (V)

20 40 60 80 100

Integ Injection current, I (m A )

Results published in IEEE Photon.Tech.Lett.2011

g gap!

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SLIDE 12
  • Single-phase wurtzite nanowires of ZnCdO with Cd up to

SUMMARY

Single-phase wurtzite nanowires of ZnCdO, with Cd up to 50%, have been demonstrated by RPE- MOCVD (C-plane

  • n sapphire)
  • Single phase wurtzite QW and thick layers of ZnMgO with
  • Single-phase wurtzite QW and thick layers of ZnMgO with

Mg up to 55% have been demonstrated by MBE B th th t h l i it f f lib i

  • Both growth technologies grow quite far from equlibrium

and Zinc vacancies are promoted

  • Proper growth coditions and substrates seem to allow

single phase WZ ZnMgCdO alloys for UV and VIS

  • ptoelectronics
  • In N doped MgZnO alloys (MOCVD) and in N:ZnO (MBE) a

shallow acceptor has been detected that seems to d t th

N V

l di t d b correspond to the NO‐VZn complex predicted by computer simulations and that may play a key role in

  • btaining robust p-type doping

the future of ZnMgCdO alloys for optoelectronics still open….

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SLIDE 13

Besides SU‐ UPM joint efforts, ….collaboration with other groups

  • 1. Centre de Recherche sur l'Hétéro‐Epitaxie et ses Applications‐CNRS (France)
  • Prof. Jean‐Michel Chauveau

Samples grown by MBE: ZnMgO with very high Mg contents and nonpolar Samples grown by MBE: ZnMgO with very high Mg contents, and nonpolar ZnMgO/ZnO MQW structures; ZnO with low residual concentrations ‐6 invited/oral presentations, ‐3 papers, ‐1 visit to UPM in 01/2013 2 Instituto Tecnológico e Nuclear (ITN Portugal) Dr Andres Redondo

  • 2. Instituto Tecnológico e Nuclear (ITN, Portugal), Dr. Andres Redondo

Analysis of ZnMgO by RBS, N‐implantation on ZnMgO; analysis of residual H in ZnO ‐2 invited presentations, ‐2 papers

  • 3. Ohio State University (EEUU), Prof. Steve Ringel

DLTS/DLOS, CV, analysis of ZnMgO and ZnO ‐1 oral presentation, ‐1 paper, ‐ OSU‐UPM Agreement on research ongoing p , p p , g g g ‐Visits to UPM in 10/2011 and 05/2012

  • 4. Univ. Valencia (Spain), Prof. Vicente Muñoz‐Sanjose

HRTEM and micro‐EDX of ZnCdO and ZnMgO samples grown by spray‐pyrolisis HRTEM and micro‐EDX of ZnCdO, and ZnMgO samples grown by spray‐pyrolisis ‐1 oral presentation, ‐2 papers ‐1 Joined MINECO‐funded project (TEC2011‐28076‐C02‐01) 5 University of Montpellier II (France) Prof Pierre Lefebvre

  • 5. University of Montpellier II (France), Prof. Pierre Lefebvre

Time resolved micro‐photoluminescence, student exchange