JEE Main levelSingle correct optionDifficulty 2 of 3ss030
Germanium doped with a trace of gallium becomes a p-type semiconductor because
Agallium makes the crystal positively charged
Bgallium has one extra electron which is free to move
Cgallium atoms create anion vacancies that trap electrons
Dgallium has one valence electron fewer than germanium's four, creating a positive hole
Answer: D
Gallium (group 13) has three valence electrons, so each Ga leaves one bond with an electron missing (a hole). Holes act as positive charge carriers, but the crystal as a whole remains electrically neutral.