Stockholders' Equity (Details) - USD ($)	3 Months Ended		12 Months Ended	84 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2015	Dec. 31, 2022	Oct. 27, 2014
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	$ 244,900,000	$ 229,846,000
Common stock options exercised	8,000
Investment in subsidiary with noncontrolling interest	203,000	(206,000)
Investment in subsidiary with redeemable noncontrolling interest	(36,000)
Noncontrolling interest portion of Tongmei stock-based compensation	17,000	10,000
Stock-based compensation	717,000	875,000
Tongmei stock-based compensation	198,000	213,000
Investment in subsidiary from noncontrolling interest		1,887,000
Net income (loss)	(3,517,000)	3,554,000
Other comprehensive income	928,000	372,000
Balance, end of period	243,418,000	236,551,000		$ 244,900,000
Reclassification adjustment from AOCI	0	0
Net income (loss) attributable to redeemable noncontrolling interests	(149,000)	418,000
Other comprehensive income attributable to redeemable noncontrolling interests	$ 70,000	46,000
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	44,000	43,000
Balance, end of period	44,000	43,000		44,000
Additional Paid-In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	235,308,000	231,622,000
Common stock options exercised	8,000
Investment in subsidiary with noncontrolling interest	(36,000)	(410,000)
Investment in subsidiary with redeemable noncontrolling interest	(36,000)
Noncontrolling interest portion of Tongmei stock-based compensation	33,000	17,000
Stock-based compensation	717,000	875,000
Tongmei stock-based compensation	198,000	213,000
Balance, end of period	236,192,000	232,317,000		235,308,000
Accumulated Deficit
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(14,159,000)	(29,970,000)
Net income (loss)	(3,348,000)	3,165,000
Balance, end of period	(17,507,000)	(26,805,000)		(14,159,000)
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	(3,118,000)	6,302,000
Other comprehensive income	858,000	327,000
Balance, end of period	(2,260,000)	6,629,000		(3,118,000)
AXT, Inc. Stockholders' Equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	221,607,000	211,529,000
Common stock options exercised	8,000
Investment in subsidiary with noncontrolling interest	(36,000)	(410,000)
Investment in subsidiary with redeemable noncontrolling interest	(36,000)
Noncontrolling interest portion of Tongmei stock-based compensation	33,000	17,000
Stock-based compensation	717,000	875,000
Tongmei stock-based compensation	198,000	213,000
Net income (loss)	(3,348,000)	3,165,000
Other comprehensive income	858,000	327,000
Balance, end of period	220,001,000	215,716,000		221,607,000
Noncontrolling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, beginning of period	23,293,000	18,317,000
Investment in subsidiary with noncontrolling interest	239,000	204,000
Noncontrolling interest portion of Tongmei stock-based compensation	(16,000)	(7,000)
Investment in subsidiary from noncontrolling interest		1,887,000
Net income (loss)	(169,000)	389,000
Other comprehensive income	70,000	45,000
Balance, end of period	$ 23,417,000	$ 20,835,000		$ 23,293,000