Q. The recombination in indirect band-gap semiconductors is slow.

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Q. Calculate the radioactive minority carrier lifetime in gallium arsenide when the minority carriers are electrons injected into a p-type semiconductor region which has a hole concentration of 10¹⁸ cm⁻³. The recombination coefficient for gallium arsenide is 7.21*10⁻¹⁰ cm³s⁻¹.

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Q. Which impurity is added to gallium phosphide to make it an efficient light emitter?

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Q. Population inversion is obtained at a p-n junction by __________

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Q. A GaAs injection laser has a threshold current density of 2.5*10³ Acm⁻² and length and width of the cavity is 240 μm and 110 μm respectively. Find the threshold current for the device.

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Q. A GaAs injection laser with an optical cavity has refractive index of 3.6. Calculate the reflectivity for normal incidence of the plane wave on the GaAs-air interface.

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Q. A homo-junction is an interface between two adjoining single-crystal semiconductors with different band-gap energies.

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Q. How many types of hetero-junctions are available?

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Q. The ______________ system is best developed and is used for fabricating both lasers and LEDs for the shorter wavelength region.

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Q. Stimulated emission by recombination of injected carriers is encouraged in __________

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Q. In semiconductor injection laser, narrow line bandwidth is of the order?

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Q. Injection laser have a high threshold current density of __________

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Q. ηᴛ is known as slope quantum efficiency.

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Q. The total efficiency of an injection laser with GaAs active region is 12%. The applied voltage is 3.6 V and band gap energy for GaAs is 2.34 eV. Determine external power efficiency.

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Q. In a DH laser, the sides of cavity are formed by _______________

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Q. A particular laser structure is designed so that the active region extends the edges of devices.

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Q. Gain guided laser structure are __________

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Q. Laser modes are generally separated by few __________

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Q. The spectral width of emission from the single mode device is __________

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Q. Single longitudinal mode operation is obtained by __________

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