III-Nitride Self-assembled Nanowire Light Emitting Diodes and Lasers on (001) Silicon.

Disks-in-nanowire;Molecular beam epitaxy;Laser on silicon;Visible nanowire LEDs;Electrical Engineering;Engineering;Electrical Engineering

Jahangir, ShafatZhong, Zhaohui ;

University of Michigan

关键词: Disks-in-nanowire;    Molecular beam epitaxy;    Laser on silicon;    Visible nanowire LEDs;    Electrical Engineering;    Engineering;    Electrical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/111490/shafat_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Substantial research is being devoted to the development of III-nitride light emitting diodes (LEDs) and lasers, which have numerous applications in solid state lighting. In particular, white LEDs play an increasingly important role in our daily lives. Current commercially available white LEDs are nearly all phosphor-converted, but these have some serious disadvantages. Planar quantum well (QW) devices on foreign substrates exhibit large threading dislocation densities, strong strain induced polarization field, and In-rich nanoclusters resulting in poor electron-hole wavefunction overlap, large emission peak shift with injection, and large efficiency drop at high injection currents in LEDs and large threshold current densities in lasers. The objective of this doctoral research is to investigate the prospects of self-assembled InGaN/GaN disks-in-nanowire (DNW) LEDs and lasers for solid state lighting. The research described here embodies a detailed study of the optical and structural characteristics of the nanowire heterostructures by varying the growth conditions and by surface passivation, and using the disks as the active region in high performance nanowire LEDs and gain medium in nanowire lasers on (001) silicon. Self-assembled InGaN/GaN DNWs are grown in a plasma-assisted molecular beam epitaxy (PA-MBE) system. Due to their large surface to volume ratio, the growth optimized and surface passivated DNWs on (001) silicon are relatively free of extended defects and have smaller polarization field resulting in higher radiative efficiencies. Blue-, green- and red-emitting DNW LEDs, with optimized nanowire densities, are demonstrated with reduced efficiency droop and smaller peak shift with injection. Phosphor-free white nanowire LEDs are realized by incorporating InGaN/GaN disks with different color emissions in the active region. The first ever monolithic edge-emitting electrically pumped green and red nanowire lasers on (001) silicon are demonstrated using DNWs as the gain media and are characterized by low threshold current densities of 1.76-2.88 kA/cm2, small peak shifts of 11-14.8 nm, large T0 of 234 K and large differential gain of 3x10-17 cm-2. Dynamic measurements performed on these lasers yield a maximum small signal modulation bandwidth of 5.8 GHz, extremely low value of chirp (0.8 Å) and a near-zero linewidth enhancement factor at the peak emission wavelength.