{"id":84629,"date":"2025-06-01T02:42:00","date_gmt":"2025-06-01T02:42:00","guid":{"rendered":"https:\/\/exam.pscnotes.com\/mcq\/?p=84629"},"modified":"2025-06-01T02:42:00","modified_gmt":"2025-06-01T02:42:00","slug":"when-a-piece-of-pure-silicon-is-doped-with-aluminium-then","status":"publish","type":"post","link":"https:\/\/exam.pscnotes.com\/mcq\/when-a-piece-of-pure-silicon-is-doped-with-aluminium-then\/","title":{"rendered":"When a piece of pure silicon is doped with aluminium, then"},"content":{"rendered":"

When a piece of pure silicon is doped with aluminium, then<\/p>\n

[amp_mcq option1=”the conductivity of the doped silicon piece will remain the same” option2=”the doped silicon piece will become n-type” option3=”the doped silicon piece will become p-type” option4=”the resistivity of the doped silicon piece will increase” correct=”option3″]<\/p>\n

\n
\n
This question was previously asked in<\/div>\n
UPSC CDS-1 – 2017<\/div>\n<\/div>\n
Download PDF<\/a>Attempt Online<\/a><\/div>\n<\/div>\n
\nThe correct answer is C) the doped silicon piece will become p-type.
\n<\/section>\n
\nPure silicon is a semiconductor with a valence of four. Aluminium is a Group 13 element and acts as a trivalent impurity (valence of three) when doped into silicon. When a trivalent impurity replaces a silicon atom in the crystal lattice, it creates a ‘hole’ (absence of an electron) in the covalent bond structure. These holes act as positive charge carriers, making the doped semiconductor p-type.
\n<\/section>\n
\nDoping semiconductors with impurities increases their conductivity. Doping with trivalent impurities creates p-type semiconductors (majority carriers are holes), while doping with pentavalent impurities (like Phosphorus or Arsenic from Group 15) creates n-type semiconductors (majority carriers are electrons). Resistivity is the inverse of conductivity, so doping decreases resistivity.
\n<\/section>\n","protected":false},"excerpt":{"rendered":"

When a piece of pure silicon is doped with aluminium, then [amp_mcq option1=”the conductivity of the doped silicon piece will remain the same” option2=”the doped silicon piece will become n-type” option3=”the doped silicon piece will become p-type” option4=”the resistivity of the doped silicon piece will increase” correct=”option3″] This question was previously asked in UPSC CDS-1 … <\/p>\n

Detailed SolutionWhen a piece of pure silicon is doped with aluminium, then<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1087],"tags":[1101,1200,1128],"class_list":["post-84629","post","type-post","status-publish","format-standard","hentry","category-upsc-cds-1","tag-1101","tag-conductivity","tag-physics","no-featured-image-padding"],"yoast_head":"\nWhen a piece of pure silicon is doped with aluminium, then<\/title>\n<meta name=\"description\" content=\"The correct answer is C) the doped silicon piece will become p-type. Pure silicon is a semiconductor with a valence of four. Aluminium is a Group 13 element and acts as a trivalent impurity (valence of three) when doped into silicon. When a trivalent impurity replaces a silicon atom in the crystal lattice, it creates a 'hole' (absence of an electron) in the covalent bond structure. These holes act as positive charge carriers, making the doped semiconductor p-type.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/exam.pscnotes.com\/mcq\/when-a-piece-of-pure-silicon-is-doped-with-aluminium-then\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"When a piece of pure silicon is doped with aluminium, then\" \/>\n<meta property=\"og:description\" content=\"The correct answer is C) the doped silicon piece will become p-type. Pure silicon is a semiconductor with a valence of four. Aluminium is a Group 13 element and acts as a trivalent impurity (valence of three) when doped into silicon. When a trivalent impurity replaces a silicon atom in the crystal lattice, it creates a 'hole' (absence of an electron) in the covalent bond structure. 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