The electric field (assumed to be one-dimensional) between two points A and B is shown. Let $$\psi_A$$ and $$\psi_B$$ be the electrostatic potentials at A and B, respectively. The value of $$\psi_A$$ − $$\psi_B$$ in Volts is ________.

Consider two BJT's biased at the same collector current with area A₁ = 0.2 μm × 0.2 μm and A₂ = 300 μm × 300 μm. Assuming that all other device parameters are identical, kT/q = 26 mV, the intrinsic carrier concentration is 1 × 10¹⁰ cm^-3, and q = 1.6 × 10^-19 C, the difference between the base-emitter voltages (in mV) of the two BJT's (i.e., V_BE1 – V_BE2) is___________.

The cut-off wavelength (in µm) of light that can be used for intrinsic excitation of a semiconductor material of bandgap E_g= 1.1 eV is ________.

Consider a silicon sample doped with N_D = 1×10¹⁵/cm³ donor atoms. Assume that the intrinsic carrier concentration n_i = 1.5×10¹⁰/cm³. If the sample is additionally doped with N_A = 1×10¹⁸/cm³ acceptor atoms, the approximate number of electrons/cm³ in the sample, at T=300 K, will be _________________.