Publications by Michael Johnston


Intrinsic quantum confinement in formamidinium lead triiodide perovskite

Nature Materials Nature Research (0)

L Herz, M Johnston


Light absorption and recycling in hybrid metal halide perovskites photovoltaic devices

Advanced Energy Materials Wiley (0)

M Johnston, T Crothers, K Lohmann, H Snaith, A Wright, N Noel, L Herz, E al., J Patel, C Xia, J Ball, K Peng

The production of highly efficient single‐ and multijunction metal halide perovskite (MHP) solar cells requires careful optimization of the optical and electrical properties of these devices. Here, precise control of CH3NH3PbI3 perovskite layers is demonstrated in solar cell devices through the use of dual source coevaporation. Light absorption and device performance are tracked for incorporated MHP films ranging from ≈67 nm to ≈1.4 µm thickness and transfer‐matrix optical modeling is utilized to quantify optical losses that arise from interference effects. Based on these results, a device with 19.2% steady‐state power conversion efficiency is achieved through incorporation of a perovskite film with near‐optimum predicted thickness (≈709 nm). Significantly, a clear signature of photon reabsorption is observed in perovskite films that have the same thickness (≈709 nm) as in the optimized device. Despite the positive effect of photon recycling associated with photon reabsorption, devices with thicker (>750 nm) MHP layers exhibit poor performance owing to competing nonradiative charge recombination in a “dead‐volume” of MHP. Overall, these findings demonstrate the need for fine control over MHP thickness to achieve the highest efficiency cells, and accurate consideration of photon reabsorption, optical interference, and charge transport properties.


Wavelength shifting of adjacent quantum wells in V-groove quantum wire structure by selective implantation and annealing

JOURNAL OF APPLIED PHYSICS 87 (2000) 1566-1568

XQ Liu, W Lu, XS Chen, SC Shen, HH Tan, S Yuan, C Jagadish, MB Johnston, LV Dao, M Gal, J Zou, DJH Cockayne


Carrier capture and relaxation in Stranski-Krastanow InxGa1-xAs/GaAs(311)B quantum dots

PHYSICAL REVIEW B 62 (2000) 2737-2742

C Lobo, N Perret, D Morris, J Zou, DJH Cockayne, MB Johnston, M Gal, R Leon


Influence on GaAs/AlGaAs quantum well infrared photodetector of proton implantation and rapid thermal annealing

JOURNAL OF INFRARED AND MILLIMETER WAVES 19 (2000) 25-28

N Li, W Lu, N Li, XQ Liu, XZ Yuan, HF Dou, XC Shen, L Fu, HH Tan, C Jagadish, MB Johnston, M Gal


Enhanced coherent terahertz emission from indium arsenide in the presence of a magnetic field

Applied Physics Letters 76 (2000) 2038-2040

R McLaughlin, A Corchia, MB Johnston, Q Chen, CM Ciesla, DD Arnone, GAC Jones, EH Linfield, AG Davies, M Pepper

We demonstrate enhancement of terahertz (THz) emission from indium arsenide at 170 K in magnetic fields (B) up to 8 T. An order of magnitude increase in visible to terahertz conversion efficiency was observed, with no suggestion of saturation of the TE polarization at higher magnetic fields. Free-space electro-optic sampling measurements confirmed the coherent nature of this radiation over the field range investigated, and gave an insight into the carrier motion subsequent to photoexcitation, which may be responsible for the observed THz power enhancement. © 2000 American Institute of Physics.


Quantum well intermixing in InGaAs/(Al)GaAs by As and H irradiation

Conference on Optoelectronic and Microelectronic Materials and Devices, Proceedings, COMMAD (1999) 355-357

L Fu, HH Tan, C Jagadish, MB Johnston, M Gal

As and H irradiation with subsequent thermal annealing were used to investigate the intermixing of InGaAs/GaAs and InGaAs/AlGaAs quantum wells (QWs). Large photoluminescence (PL) energy shifts were observed in both materials. Due to dynamic annealing in AlGaAs and the presence of Al in the barriers, the InGaAs/AlGaAs samples showed better PL intensities recovery and larger energy shifts than the InGaAs/GaAs samples after both As and H irradiation. Larger energy shifts were obtained for As irradiation at lower doses than when compared to H irradiation. However, at higher doses H irradiation resulted in higher energy shift than As irradiation. Results of the effect of irradiation temperature showed that higher shift could be obtained with increasing temperature for As irradiation at lower doses while for H irradiation, implant temperature had little effect.


Possibility of enhanced frequency response of intermixed InGaAs/GaAs and InGaAs/AlGaAs quantum well devices

Conference on Optoelectronic and Microelectronic Materials and Devices, Proceedings, COMMAD (1999) 352-354

LV Dao, MB Johnston, M Gal, L Fu, HH Tan, C Jagadish

Photoluminescence up conversion study of the intermixed InGaAs/GaAs and InGaAs/AlGaAs quantum wells showed that the capture of photo-excited carriers into the intermixed quantum wells is faster (25 ps) than capture into the non-intermixed quantum wells (45 ps). The reasons for this significant reduction in the capture time is related to modification of the shape of the intermixed quantum wells.


Proton irradiation-induced intermixing in InGaAs/(Al)GaAs quantum wells and quantum-well lasers

JOURNAL OF APPLIED PHYSICS 85 (1999) 6786-6789

L Fu, HH Tan, MB Johnston, M Gal, C Jagadish


Proton implantation and rapid thermal annealing effects on GaAs/AlGaAs quantum well infrared photodetectors

SUPERLATTICES AND MICROSTRUCTURES 26 (1999) 317-324

N Li, N Li, W Lu, XQ Liu, XZ Yuan, ZF Li, HF Dou, SC Shen, Y Fu, M Willander, L Fu, HH Tan, C Jagadish, MB Johnston, M Gal


Interdiffused quantum-well infrared photodetectors for color sensitive arrays

APPLIED PHYSICS LETTERS 75 (1999) 923-925

MB Johnston, M Gal, N Li, ZH Chen, XQ Liu, N Li, W Lu, SC Shen, L Fu, HH Tan, C Jagadish


Si and C delta-doping of GaAs grown by metal organic vapour phase epitaxy for fabrication of nipi doping superlattices

MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY 51 (1998) 103-105

C Jagadish, G Li, MB Johnston, M Gal


Si and C delta-doping for device applications

JOURNAL OF CRYSTAL GROWTH 195 (1998) 54-57

G Li, MB Johnston, A Babinski, S Yuan, M Gal, SJ Chua, C Jagadish


Improved carrier collection in intermixed InGaAs/GaAs quantum wells

APPLIED PHYSICS LETTERS 73 (1998) 3408-3410

LV Dao, MB Johnston, M Gal, L Fu, HH Tan, C Jagadish


Photoluminescence study of the dynamical properties of GaAs sawtooth superlattices

JOURNAL OF APPLIED PHYSICS 82 (1997) 5748-5752

MB Johnston, M Gal, G Li, C Jagadish


V-grooved GaAs/AlGaAs quantum wires with side wall quantum wells intermixed by pulsed anodization and rapid thermal annealing

1996 CONFERENCE ON OPTOELECTRONIC AND MICROELECTRONIC MATERIALS AND DEVICES, PROCEEDINGS (1996) 200-203

Y Kim, S Yuan, R Leon, A Clark, C Jagadish, MB Johnston, P Burke, M Gal, J Zou, D Cockayne, MR Phillips, MAS Kalceff


Growth of Si and C delta-doped nipi doping superlattices in GaAs by metal organic vapor phase epitaxy

APPLIED PHYSICS LETTERS 69 (1996) 4218-4220

G Li, C Jagadish, MB Johnston, M Gal


Effects of anodic oxide induced intermixing on the structural and optical properties of quantum wire structure grown on nonplanar GaAs substrate

JOURNAL OF APPLIED PHYSICS 80 (1996) 5014-5020

Y Kim, S Yuan, R Leon, C Jagadish, M Gal, MB Johnston, MR Phillips, MAS Kalceff, J Zou, DJH Cockayne


Optical properties of delta-doped GaAs nipi super-lattices

1996 CONFERENCE ON OPTOELECTRONIC AND MICROELECTRONIC MATERIALS AND DEVICES, PROCEEDINGS (1996) 179-182

MB Johnston, M Gal, G Li, C Jagadish


STATIC ELECTRIFICATION BY NONWETTING LIQUIDS - CONTACT CHARGING AND CONTACT ANGLES

LANGMUIR 11 (1995) 4153-4158

VV YAMINSKY, MB JOHNSTON

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