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Lateral feeding design and selective oxidation process in vertical cavity transistor laser
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View: Figures


Image of FIG. 1.
FIG. 1.

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.

Image of FIG. 2.
FIG. 2.

The energy band diagram of the n-p-n VCTL with a detailed layer structure.

Image of FIG. 3.
FIG. 3.

The VCTL refractive index and normalized simulated field intensity profile.

Image of FIG. 4.
FIG. 4.

The schematics of three VCTL layout designs: (a) concentric aperture design, (b) lateral feeding design, and (c) lateral feeding and selective oxidation design.

Image of FIG. 5.
FIG. 5.

The scanning electron microscopic image of the selective oxidation VCTL after removing the polyimide.

Image of FIG. 6.
FIG. 6.

Oxide-VCTLs (a) the collector I-V and (b) the light L-V output characteristics of a 6.4 × 7.4 m2 and a 4.5 × 5.6 m2 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.

Image of FIG. 7.
FIG. 7.

The inset shows the equivalent circuit of collector I-V measurement set-up. The 6.4 × 7.4 m2 oxide-VCTL I-V simulated and measured characteristics to extract the total emitter resistance R.

Image of FIG. 8.
FIG. 8.

(a) The current gain β of the VCTL with a 6.4 × 7.4 m2 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 I = 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, V 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.

Image of FIG. 9.
FIG. 9.

The laser emission spectra of oxide-VCTLs with 6.4 × 7.4 m2 and 4.5 × 5.6 m2 apertures biased at I = 1.8, 2.4, and 3.6 mA, respectively.

Image of FIG. 10.
FIG. 10.

The SMSR for 6.4 × 7.4 m2 and 4.5 × 5.6 m2 devices are 29 and 37 dB, respectively.

Image of FIG. 11.
FIG. 11.

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 m2 and 0.97 nm/mA for the 4.5 × 5.6 m2.

Image of FIG. 12.
FIG. 12.

L-I characteristics of the VCTL with a 6.4 × 7.4 m2 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.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Lateral feeding design and selective oxidation process in vertical cavity transistor laser