The cross sectional schematic of an oxide-VCTL. With oxidization confinement, the electron current can only be fed through the aperture and the optical modes are confined.
The energy band diagram of the n-p-n VCTL with a detailed layer structure.
The VCTL refractive index and normalized simulated field intensity profile.
The schematics of three VCTL layout designs: (a) concentric aperture design, (b) lateral feeding design, and (c) lateral feeding and selective oxidation design.
The scanning electron microscopic image of the selective oxidation VCTL after removing the polyimide.
Oxide-VCTLs (a) the collector IC-VCE and (b) the light L-VCE output characteristics of a 6.4 × 7.4 μm2 and a 4.5 × 5.6 μm2 for base current biased from 0 to 3mA. The measured threshold is 1.3 and 1.6 mA for the large and small devices, respectively.
The inset shows the equivalent circuit of collector I-V measurement set-up. The 6.4 × 7.4 μm2 oxide-VCTL IC-VCE simulated and measured characteristics to extract the total emitter resistance RE.
(a) The current gain β of the VCTL with a 6.4 × 7.4 μm2 aperture as a function of base current at 20 and −90 °C. At −90 °C, the current gain shows a decreasing trend with increasing base current indicating reduction of radiative recombination lifetime, spectrum narrowing and lasing at IB,TH = 1.3 mA. (b) The spontaneous emission spectra of the VCTL below threshold at −90 and 20 °C, to ensure the transistor is operating in forward-active mode, VCE is set at 3.5 V. The spontaneous spectrum shows narrowing of 0.18 nm at −90 °C as compared with 1.41 nm at the 20 °C spectrum.
The laser emission spectra of oxide-VCTLs with 6.4 × 7.4 μm2 and 4.5 × 5.6 μm2 apertures biased at IB = 1.8, 2.4, and 3.6 mA, respectively.
The SMSR for 6.4 × 7.4 μm2 and 4.5 × 5.6 μm2 devices are 29 and 37 dB, respectively.
The oxide-VCTL emission peak shifts with base current. The solid circles and squares are the measured data points, and the dashed lines are fitted relationship. As the base current increases, the emission shows a red-shift due to junction heating. The shifts are 0.68 nm/mA for the 6.4 × 7.4 μm2 and 0.97 nm/mA for the 4.5 × 5.6 μm2.
L-IB characteristics of the VCTL with a 6.4 × 7.4 μm2 aperture under different ambient temperatures, from −90 °C to −45 °C. The inset shows the shift of threshold current for the 2 VCTLs. The threshold current exhibits an exponential increase with increasing temperature.
Article metrics loading...
Full text loading...