Match the following:

1. With increase in temperature Fermi-level tries to come in between the energy gap exactly at middle
2. Mobility of electron in GaAs is very high compared to mobility of hole
3. In LED, the light energy radiated due to recombination with the aid of traps.

1. DPSK demodulator requires a device which operates at carrier frequency and provides a delay of bit time T_b
2. In DPSK, synchronous demodulation recovers the signal b(t) and the decoding of b(t) to generate d(t) is done at base band
3. In both DPSK and DEPSK errors always occur in pairs

1. f₁ = ∑m (1, 2, 4, 8, 10, 14)
2. f₂ = ∑m (2, 5, 9, 15)
3. f₃ = ∑m (2, 4, 5, 6, 7)

1. higher emission efficiency
2. no tuning arrangement
3. narrow spectral width
4. provision for confinement