An InP-based quantum cascade laser heterostructure emitting at 3.76 μm is grown with gas-source molecular beam epitaxy. The laser core is composed of strain balanced In0.76Ga0.24As/In0.26Al0.74As. Pulsed testing at room temperature exhibits a low threshold current density (1.5 kA/cm2) and high wall plug efficiency (10%). Room temperature continuous wave operation gives 6% wall plug efficiency with a maximum output power of 1.1 W. Continuous wave operation persists up to 95 °C.

The performance of LEDs with Ga-doped ZnO (Ga:ZnO) and Sn-doped In 2 O 3 (ITO) current-spreading layers (CSLs) has been evaluated at high injection current densities. LEDs with electron beam-hydrothermally deposited Ga:ZnO transparent CSLs showed improved performance compared to electron beam deposited ITO at all current densities. External quantum efficiency and wall plug efficiency were both higher for blue emitting LEDs with ZnO. Luminous efficacy increased greatly for the ZnO-based CSL with a peak value of 113 lm/W compared to 82 lm/W for the ITO-based CSL, a 37% improvement.

Device highlights  Demonstrated the first continuous wave LAE-ZnO () blue laser diode at UCSB  Demonstrated the first hydrothermally grown ZnO top clad () blue InGaN/GaN laser diode  Demonstrated the first ITO top clad limited area epitaxy () blue InGaN/GaN laser diode  Enhanced high current density device performance of GaN LEDs at by replacing ITO current spreading layer with ZnO:Ga Material growth and characterization  Performed MOCVD epitaxial growth of InGaN and AlGaN based blue and green laser diodes on LAE patterned semipolar GaN substrates  Developed and performed aqueous solution growth of ZnO transparent conducting oxide (TCO) for laser diode cladding and LED current spreading layers  Executed structural, optical and electrical characterization of MOCVD grown III-nitride material using X-ray diffraction (XRD), reciprocal space maps (RSMs), photoluminescence (PL), Cathodoluminescence (CL), fluorescence microscopy (FM), electroluminescence (EL), and secondary ion mass spectroscopy (SIMS)  Conducted full laser diode electrical and optical device characterization Laser diode processing and fabrication  Processed semipolar GaN substrates for limited area epitaxy (LAE)  Processed semipolar GaN-based edge emitting lasers with etched and polished facets  Improved dicing process for polished facet laser fabrication to increase device yield Device optical modeling and design  Employed Fimmwave software to simulate the effect of cladding and waveguide design on the optical modes of TCO top clad () GaN lasers in the blue and green spectral regions viii  Evaluated the performance of ZnO compared to ITO as the TCO top cladding layer for the design permutations of () GaN lasers in the blue and green spectral regions

Incorporating transparent conducting oxide (TCO) top cladding layers into III-nitride laser diodes (LDs) improves device design by reducing the growth time and temperature of the p-type layers. We investigate using ZnO instead of ITO as the top cladding TCO of a semipolar (202¯1) III-nitride LD. Numerical modeling indicates that replacing ITO with ZnO reduces the internal loss in a TCO clad LD due to the lower optical absorption in ZnO. Lasing was achieved at 453 nm with a threshold current density of 8.6 kA/cm and a threshold voltage of 10.3 V in a semipolar (202¯1) III-nitride LD with ZnO top cladding.

Phone/Fax: þ8565057650Group III impurity doped ZnO thin films were deposited on MgAl 2 O 3 substrates using a simple low temperature two-step deposition method involving atomic layer deposition and hydrothermal epitaxy. Films with varying concentrations of either Al, Ga, or In were evaluated for their optoelectronic properties. Inductively coupled plasma atomic emission spectroscopy was used to determine the concentration of dopants within the ZnO films. While Al and Ga-doped films showed linear incorporation rates with the addition of precursors salts in the hydrothermal growth solution, In-doped films were shown to saturate at relatively low concentrations. It was found that Ga-doped films showed the best performance in terms of electrical resistivity and optical absorbance when compared to those doped with In or Al, with a resistivity as low as 1.9 mΩ cm and an optical absorption coefficient of 441 cm À1 at 450 nm.