Prof. Steve DenBaars

University of California

Prof. Steve DenBaars

University of California

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Academic Career Length

41Years (1986-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 April 2009 in Nature Photonics

Journal Article

Prospects for LED lighting

Siddha Pimputkar

James S. Speck

Steve DenBaars

Shuji Nakamura

6 December 1993 in Applied Physics Letters

Journal Article

Direct formation of quantum-sized dots from uniform coherent islands of InGaAs on GaAs surfaces

D. Leonard

M. Krishnamurthy

C. M. Reaves

Steve DenBaars

P. M. Petroff

The 2D–3D growth mode transition during the initial stages of growth of highly strained InGaAs on GaAs is used to obtain quantum‐sized dot structures. Transmission electron micrographs reveal that when the growth of In_0.5Ga_0.5As is interrupted exactly at the onset of this 2D–3D transition, dislocation‐free islands (dots) of the InGaAs result. Size distributions indicate that these dots are ∼300 Å in diameter and remarkably uniform to within 10% of this average size. The areal dot densities can be varied between 10⁹ and 10¹¹ cm⁻². The uniformity of the dot sizes is explained by a mechanism based on reduction in adatom attachment probabilities due to strain. We unambiguously demonstrate photoluminescence at ∼1.2 eV from these islands by comparing samples with and without dots. The luminescent intensities of the dots are greater than or equal to those of the underlying reference quantum wells.

9 February 2004 in Applied Physics Letters

Journal Article

Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening

T. Fujii

Y. Gao

R. Sharma

E. L. Hu

Steve DenBaars

S. Nakamura

Roughened surfaces of light-emitting diodes (LEDs) provide substantial improvement in light extraction efficiency. By using the laser-lift-off technique followed by an anisotropic etching process to roughen the surface, an n-side-up GaN-based LED with a hexagonal “conelike” surface has been fabricated. The enhancement of the LED output power depends on the surface conditions. The output power of an optimally roughened surface LED shows a twofold to threefold increase compared to that of an LED before surface roughening.

30 June 2000 in Applied Physics Letters

Journal Article

Polarization effects, surface states, and the source of electrons in AlGaN/GaN heterostructure field effect transistors

J. P. Ibbetson

P. T. Fini

K. D. Ness

Steve DenBaars

J. S. Speck

U. K. Mishra

The origin of the two-dimensional electron gas (2DEG) in AlGaN/GaN heterostructure field effect transistors is examined theoretically and experimentally. Based on an analysis of the electrostatics, surface states are identified as an important source of electrons. The role of the polarization-induced dipole is also clarified. Experimental Hall data for nominally undoped

{Al}_{0.34} {Ga}_{0.66} N/GaN

structures indicate that ∼1.65 eV surface donors are the actual source of the electrons in the 2DEG, which forms only when the barrier thickness exceeds 35 Å.

29 January 1996 in Applied Physics Letters

Journal Article

Role of threading dislocation structure on the x-ray diffraction peak widths in epitaxial GaN films

B. Heying

X. H. Wu

S. Keller

Y. Li

D. Kapolnek

J. S. Speck

In this letter we demonstrate that the anomalously low (002) x‐ray rocking curve widths for epitaxial hexagonal GaN films on (001) sapphire are a result of a specific threading dislocation (TD) geometry. Epitaxial GaN films were grown on c‐plane sapphire by atmospheric pressure metalorganic chemical vapor deposition (MOCVD) in a horizontal flow reactor. Films were grown with (002) rocking curves (ω‐scans) widths as low as 40 arcsec and threading dislocation densities of ∼2×10¹⁰ cm⁻². The threading dislocations in this film lie parallel to the [001] direction and within the limit of imaging statistics, all are pure edge with Burgers vectors parallel to the film/substrate interface. These TDs will not distort the (002) planes. However, distortion of asymmetric planes, such as (102), is predicted and confirmed in (102) rocking curve widths of 740 arcsec. These results are compared with films with (002) rocking curves of ∼270 arcsec and threading dislocation densities of ∼7×10⁸ cm⁻².

3 November 1997 in Applied Physics Letters

Journal Article

Absorption coefficient, energy gap, exciton binding energy, and recombination lifetime of GaN obtained from transmission measurements

J. F. Muth

J. H. Lee

I. K. Shmagin

R. M. Kolbas

H. C. Casey

Steve DenBaars

The absorption coefficient for a 0.4-μm-thick GaN layer grown on a polished sapphire substrate was determined from transmission measurements at room temperature. A strong, well defined exciton peak for the

A

and

B

excitons was obtained. The

A

B

, and

C

excitonic features are clearly defined at 77 K. At room temperature, an energy gap

E_{g} =3.452±0.001 eV

and an exciton binding energy

E_{x}^{A,B} =20.4±0.5 meV

for the

A

and

B

excitons and

E_{x}^{C} =23.5±0.5 meV

for the

C

exciton were determined by analysis of the absorption coefficient. From this measured absorption coefficient, together with the detailed balance approach of van Roosbroek and Shockley, the radiative constant

{B=1.1×10}^{−8} {cm}^{3} /s

was obtained.

About Me

Biographie : Dr. Steven P. DenBaars is a Professor of Materials and Co-Director of the Solid-State Lighting and Energy Electronics Center (SSLEEC) at the University of California Santa Barbara. In 1988 he obtained a Ph.D. Electrical Engineering from the University of Southern California, MS Materials Science, in 1986, and BS in Materials and Metallurgical Engineering, from the University of Arizona 1984. Dr. DenBaars started his 30 career in semiconductors at Hewlett-Packard in 1988, and joined UCSB in 1991. In 2005 he was appointed the Mitsubishi Chemical Chair in Solid State Lighting and Displays. Specific research interests include growth of wide-bandgap semiconductors (GaN based), and their application to Blue LEDs and lasers and high power electronic devices. Prof. DenBaars has been very active in entrepreneurship, having helped co-found several start-up companies in the field of photonics and electronics. In 1996 he Co-founded Nitres Inc. along with Dr. Umesh Mishra which was the first GaN LED start-up in US. Nitres was acquired by Cree Inc. for $220 million in May 2000. In 2008 he Co-Founded Soraa Inc. along with Professor Nakamura and Speck to commercialize highly efficient LED lighting. In 2013 he Co-Founded SLD Laser, along with Professor Nakamura, Dr. James Raring, and Dr. Paul Rudy to pioneer blue lasers and laser lighting products. Acting as the CEO and Chairman he helped build the company to over $20 million in revenue and 150 employees before being acquired

Prof. Steve DenBaars

Prof. Steve DenBaars

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