Stockholders' Equity (Details) - USD ($)	3 Months Ended		12 Months Ended	96 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2015	Dec. 31, 2023	Oct. 27, 2014
Stockholders' Equity
Balance, beginning of period	$ 227,483,000	$ 244,900,000
Common stock options exercised	20,000	(8,000)
Investment in subsidiary with noncontrolling interest		203,000
Investment in subsidiary with redeemable noncontrolling interest		(36,000)
Noncontrolling interest portion of Tongmei stock-based compensation	(11,000)	17,000
Stock-based compensation	614,000	717,000
Tongmei stock-based compensation	195,000	198,000
Net loss	(1,977,000)	(3,517,000)
Other comprehensive income (loss)	(1,814,000)	928,000
Balance, end of period	224,510,000	243,418,000		$ 227,483,000
Reclassification adjustment from AOCI	0	0
Net income (loss) attributable to redeemable noncontrolling interests	(71,000)	(149,000)
Other comprehensive loss attributable to redeemable noncontrolling interests	$ (189,000)	70,000
Stock repurchase program, authorized amount					$ 5,000,000.0
Shares repurchased (in shares)	0		908,000	0
Average price of shares repurchased (in dollars per share)			$ 2.52
Total purchase price			$ 2,300,000
Stock repurchase program remaining authorized repurchase amount	$ 2,700,000
Preferred Stock
Stockholders' Equity
Balance, beginning of period	3,532,000	3,532,000
Balance, end of period	3,532,000	3,532,000		$ 3,532,000
Common Stock
Stockholders' Equity
Balance, beginning of period	44,000	44,000
Balance, end of period	44,000	44,000		44,000
Additional Paid-In Capital
Stockholders' Equity
Balance, beginning of period	238,452,000	235,308,000
Common stock options exercised	20,000	(8,000)
Investment in subsidiary with noncontrolling interest		(36,000)
Investment in subsidiary with redeemable noncontrolling interest		(36,000)
Noncontrolling interest portion of Tongmei stock-based compensation	(24,000)	33,000
Stock-based compensation	614,000	717,000
Tongmei stock-based compensation	195,000	198,000
Balance, end of period	239,257,000	236,192,000		238,452,000
Accumulated Deficit
Stockholders' Equity
Balance, beginning of period	(32,040,000)	(14,159,000)
Net loss	(2,083,000)	(3,348,000)
Balance, end of period	(34,123,000)	(17,507,000)		(32,040,000)
Accumulated Other Comprehensive Income (Loss)
Stockholders' Equity
Balance, beginning of period	(5,999,000)	(3,118,000)
Other comprehensive income (loss)	(1,627,000)	858,000
Balance, end of period	(7,626,000)	(2,260,000)		(5,999,000)
AXT, Inc. Stockholders' Equity
Stockholders' Equity
Balance, beginning of period	203,989,000	221,607,000
Common stock options exercised	20,000	(8,000)
Investment in subsidiary with noncontrolling interest		(36,000)
Investment in subsidiary with redeemable noncontrolling interest		(36,000)
Noncontrolling interest portion of Tongmei stock-based compensation	(24,000)	33,000
Stock-based compensation	614,000	717,000
Tongmei stock-based compensation	195,000	198,000
Net loss	(2,083,000)	(3,348,000)
Other comprehensive income (loss)	(1,627,000)	858,000
Balance, end of period	201,084,000	220,001,000		203,989,000
Noncontrolling Interests
Stockholders' Equity
Balance, beginning of period	23,494,000	23,293,000
Investment in subsidiary with noncontrolling interest		239,000
Noncontrolling interest portion of Tongmei stock-based compensation	13,000	(16,000)
Net loss	106,000	(169,000)
Other comprehensive income (loss)	(187,000)	70,000
Balance, end of period	$ 23,426,000	$ 23,417,000		$ 23,494,000