Projects at the EPFL Center of MicroNanoTechnology

III-NITRIDE BASED BLUE VCSELS

G. Cosendey, A. Castiglia, G. Rossbach, J.-F. Carlin, N. Grandjean (SB-IPHYS-LASPE)Laboratory of Advanced Semiconductors for Photonics and Electronics, EPFL

Project objective:Highly-reflective dielectric-based distributed Bragg reflectors (DBRs) have been developed (Fig. 1) to serve as top mirror in blue vertical cavity surface emitting lasers (VCSELs). A schematic drawing and an SEM cross-section view of such a device are depicted in Fig. 2 and Fig. 3, respectively. Electroluminescence (EL) spectra measured below and above threshold on a blue VCSEL are shown in Fig. 4.

200 250 300 350 400 450 500 550 6000

20

40

60

80

100

R T A = 1-(R+T)

R, T

, A (%

)

Wavelength (nm)

137 nm

Rmax = 99.7%

Stopband width:

Top dielectric DBR

Bottom InAlN/GaN DBR

Metal pads

Figure 1: Reflection R and transmission T of a 7-pair SiO2/TiO2 DBR.

Figure 2: Schematic drawing of a monolithic nitride-based VCSEL.

1 mm10 mm 400 410 420 430 440

EL in

tens

ity (a

rb. u

nit)

Wavelength (nm)

0.5 Ith Ith

Cavity (lasing) mode

Bragg modes

Figure 3: SEM cross-section view of a processed VCSEL.

Figure 4: VCSEL EL spectra below and at lasing threshold.

Techniques employed: E-beam evaporator (LAB600) for dielectric DBR deposition.Publications:[1] G. Cosendey, A. Castiglia, G. Rossbach, J.-F. Carlin, and N. Grandjean, Blue monolithic

AlInN-based vertical cavity surface emitting laser diode on free-standing GaN substrate, Appl. Phys. Lett. 101, 151113 (2012).

[2] G. Cosendey, J.-F. Carlin, N. A. K. Kaufmann, R. Butté, and N. Grandjean, Strain compensation in AlInN/GaN multilayers on GaN substrates: Application to the realization of defect-free Bragg reflectors, Appl. Phys. Lett. 98, 181111 (2011).

Funding: NCCR QP, FNS, CTI/KTI.

1