UV VISOPTOELECTRONICS WITHOXIDES - JST...CV profiling using Schottky diodes 3.33.43.53.6 Photon...
Transcript of UV VISOPTOELECTRONICS WITHOXIDES - JST...CV profiling using Schottky diodes 3.33.43.53.6 Photon...
UV VIS OPTOELECTRONICS WITH OXIDESADRIAN HIERRO, ELIAS MUÑOZ
UV‐VIS OPTOELECTRONICS WITH OXIDES
INSTITUTE OF SYSTEMS BASED ON OPTOELECTRONICS AND MICROTECHNOLOGYELECTRONICS ENGINEERING DEPT.
UNIVERSIDAD POLITECNICA DE MADRID (UPM), MADRID, SPAINUNIVERSIDAD POLITECNICA DE MADRID (UPM), MADRID, SPAIN
A. Nakamura and J. TemmyoResearch Institute of Electronics Shizuoka University HamamatsuResearch Institute of Electronics, Shizuoka University, Hamamatsu
JOINT JST‐MINECO PROJECT, SU‐UPM collaboration
From “Wide bandgap semiconductors”, Springer 2007.K. Takahashi, A. Yoshikawa, A. Sandhu, editors. 162 Committee JSPS
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?
outline• 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 LEDMQW nCdO/p type SiC green
• Summary/reflections
Zn(Mg,Cd)O:N by RPE‐MOCVD
Plasma spectrum in situRF13 56MHRemote plasma Heater 10KHz
A. Nakamura, J. Temmyo, Shizuoka U.
OH O2 plasma/ H2 carrier
Plasma spectrum in situRF13.56MHz
Oxygen/HydrogenNitrogen
O
H
y (a
rb. u
nits
)
OH
substrate
MeCp2Mg(EtCp2Mg)
susceptor
O2 plasma/ N2 carrier
O2
N2
N2
N2
NOInte
nsityDEZn
DMCd
H2/N2
MBP/RPGrowth conditions:Pressure: 0.1TorrTemp: 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
66
STRUCTURAL and OPTICAL PROPERTIES of ZnCdONANOCOLUMNS
‐ 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 nmHRTEM
V.Muñoz, U.Valencia, SP
ZnO
14% Cd
27% Cd
Annealed
y (a
.u)
45% Cd
PL
PL
Inte
nsity
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 (atcent
ratio
n (a
t
Cd
1. Emission demonstrated down to 2.02 eV2. 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
0.0NanowireSurface
t %)
Con
c
Nanowire Tip
Width (m) Lenght (m) Results accepted for publication in Appl.Phys.Lett.
3. State of the art ZnCdO nanocolumns!
CHARACTERIZATION of ZnMgO (MOCVD) LAYERS (SU)
0.9
1.0
d
<1120>
RBS determination of stoichiometry and quality*
1017
m-3) 5.6%Mg
DARKC‐V profiles
0.7
0.8
0.9
aliz
ed y
ield
Nd-N
a) (cm
9.5%Mg 14.5%Mg 18.0%Mg
0.5
0.6
Zn MgO
Nor
ma
a-plane MgZnO 0 15 0 30 0 45 0 60
1016
n=(N
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.00.4
O
Theta (º)
MgZnO
*Collaboration with A. Redondo, ITN, Portugal
0.15 0.30 0.45 0.60Depth (m)
Zn1-xMgxO1 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 samples2.Growth plane (a‐plane or c‐plane)does not affect Mg incorporation3 ZnMgO is highly compensated
E
Ev+580 meV
Ev+280 meVVZn (-/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 compensateddue to two acceptor levels related
to VZn4. Can use ZnMgO samples toEV
* A.F. Kohan et al. Phys.Rev.B 61, 15019 (2000)
18.0 1.27x1016 1.01x1018 5.23x1016 4. Can use ZnMgO samples toachieve p‐type doping
Same VZn related acceptors also found in MBE ZnMgOlayers from JM Chauveau, CNRS‐CRHEA, FR
Typical p‐doping resultsA. Nakamura, J. Temmyo, Shizuoka U.
n-typep-type
MgZnO:(N,In,Cu) co-doping
n-typep-type
g ( , , ) p gshowed p-type- N solubility enhanced by codoping
(N) acceptor activated- (N)O acceptor activated
against expectation:- n-type conductivity for N, Cun type conductivity for N, Cu- Conductivity-type change for N, Inwas occurred under RTA activation.
ref: morphology change after RTA200nm 200nm
As grown RTA 800oC
9
S. Mohanta, et al. J. Appl. Phys 110 (2011) 013524.
*Implanted profile (SRIM) Crystal recovery (RBS)
N‐implantation in MOCVD ZnMgO LAYERSOptical 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
on Å
150 keV N 10º
Implanted profile (SRIM) Crystal recovery (RBS)
.)
MgxZn
1-xO (as grown)(b)
x=15%x=9%
Optical emission (PL)
1500
2000
2500+500 C (10 )
+700 ºC (10') +900 ºC (10') Random
Yie
ld (c
ount
s
O
Zn
0 10
0.15
0.20
0.25 Zn+O
OVac
anci
es /
io
Zn
nsity
(a.u x=5%
x=0%
400 600 800 1000 1200 1400 16000
500
1000
YAl
0 100 200 300 400 5000.00
0.05
0.10
Depth (nm)
V
(b)
PL
inte
n
(c) MgxZn1-xO:N (+RTA 900ºC)
Energy (keV)Depth (nm)*Collaboration with A. Redondo, ITN, Portugal
CV profiling using Schottky diodes3.3 3.4 3.5 3.6
Photon energy (eV)1E18
5 % Mg 9 % Mg
Implanted + RTAm-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‐type3. Best crystal recovery found at 900°C (strong Alout‐diffusion from substrate at higher T).
h l l d l d f l
0.138 0.207 0.276 0.3451E16
as-grown
W (m)
1 KHz
4. Thermal annealing reduces Xtal damage, films areless n‐type, BUT no direct observation of p‐typebehavior ; defects overcome N‐related acceptors
MQW ZnCdO/ZnO/p‐SiC VIS LED
b. u
nit)
room temprerature
Mesa: 200m
FWHM: 690 meV
Layers grown at Shizuoka U. 5 QW ZnCdO (20% Cd)
ensi
ty (a
rb
80mA70 A
Mesa: 200m
EL
inte 70mA
60mA40mA20mA
1.5 2.0 2.5 3.0 3.5Photon 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 (a
rb. 2.55eV (agreement with
PL from ZnCdO/ZnOQW)
10-7
10-6
10-5
urre
nt d
ens
grat
ed E
L in
te2. First demonstration of ZnCdO MQW LED in literature!!....green
-4 -3 -2 -1 0 1 2 3 410-9
10-8C
Voltage (V)
0 20 40 60 80 100Inte
g
In jec tion cu rren t, I (m A )
Results published in IEEE Photon.Tech.Lett.2011
ggap!
• Single-phase wurtzite nanowires of ZnCdO with Cd up to
SUMMARYSingle-phase wurtzite nanowires of ZnCdO, with Cd up to50%, have been demonstrated by RPE- MOCVD (C-planeon sapphire)
• Single phase wurtzite QW and thick layers of ZnMgO with• Single-phase wurtzite QW and thick layers of ZnMgO withMg 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 equlibriumand Zinc vacancies are promoted
• Proper growth coditions and substrates seem to allowsingle phase WZ ZnMgCdO alloys for UV and VIS optoelectronics
• 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 bcorrespond to the NO‐VZn complex predicted bycomputer simulations and that may play a key role in obtaining robust p-type doping
the future of ZnMgCdO alloys for optoelectronics still open….
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 nonpolarSamples 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 01/20132 Instituto Tecnológico e Nuclear (ITN Portugal) Dr Andres Redondo2. 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 RingelDLTS/DLOS, CV, analysis of ZnMgO and ZnO
‐1 oral presentation, ‐1 paper, ‐ OSU‐UPM Agreement on research ongoingp , p p , g g g‐Visits to UPM in 10/2011 and 05/2012
4. Univ. Valencia (Spain), Prof. Vicente Muñoz‐SanjoseHRTEM and micro‐EDX of ZnCdO and ZnMgO samples grown by spray‐pyrolisisHRTEM 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 Lefebvre5. University of Montpellier II (France), Prof. Pierre LefebvreTime resolved micro‐photoluminescence, student exchange