With the decrease in lattice constant of a semiconductor $( \mathrm{if} {\mathrm{E}}_{\mathrm{c}}, {\mathrm{E}}_{\mathrm{g}}, {\mathrm{E}}_{\mathrm{v}}$ represent the width of conduction band, energy gap and width of valency band) 

 

• The cube's side length serves as the lattice constant. The space between the molecules or atoms that make up the lattice is represented by the word "lattice." 
• Accordingly, a drop in lattice constant often means that electrons are more closely bound to the atom and so take more energy to escape, increasing the band gap.
• On the other hand, valence (filled) and conduction (unfilled) bandwidth will both become smaller as a result of the contracting lattice parameter.

Hence the correct answer is ${\mathrm{E}}_{\mathrm{c}}, {\mathrm{E}}_{\mathrm{v}}$decrease, but ${\mathrm{E}}_{\mathrm{g}}$ increase