11. STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Mar. 31, 2022

STOCK-BASED COMPENSATION

Summary of stock option activities

			Weighted
		Number of Shares	Average	Weighted
	Shares	Underlying	Remaining	Average
	Available for	Options	Contractual	Exercise		Intrinsic
	Grant	Outstanding	Life (Years)	Price		Value
Balance at March 31, 2019	3,426,548	8,017,029		$	5.77
Granted	(1,011,708)	1,011,708		$	8.11
Exercised	—	(772,667)		$	4.39	$	2,614,879
Forfeited	107,474	(120,279)		$	7.03
Balance at March 31, 2020	2,522,314	8,135,791		$	6.17
Granted	(1,285,252)	1,285,252		$	6.46
Exercised	—	(667,503)		$	5.99	$	961,633
Forfeited	94,500	(320,663)		$	7.84
Balance at March 31, 2021	1,331,562	8,432,877		$	6.17
Options reserved	4,000,000	—		$	—
Granted	(1,280,761)	1,280,761		$	5.43
Exercised	—	(316,784)		$	5.12	$	149,937
Forfeited	484,862	(806,179)		$	6.45
Balance at March 31, 2022	4,535,663	8,590,675	5.39	$	6.07
Options vested and exercisable		5,499,074	3.77	$	5.86	$	133,784
Options vested and expected to vest		8,498,505	5.35	$	6.07	$	133,784

Schedule of options outstanding by exercise price

				Number of	Options Outstanding			Options Exercisable
				Shares	Weighted		Weighted Average		Weighted
				Underlying	Average		Remaining	Number	Average
				Options	Exercise		Contractual	Vested and	Exercise
Exercise Price				Outstanding	Price		Life (Years)	Exercisable	Price
$	3.40	-	4.81	1,013,655	$	4.12	3.58	822,845	$	4.04
$	4.98	-	4.99	1,050,501	$	4.99	3.82	1,050,501	$	4.99
$	5.13	-	5.58	1,410,456	$	5.42	6.37	630,915	$	5.24
$	5.59	-	5.83	1,167,427	$	5.76	5.57	535,873	$	5.70
$	5.91	-	6.70	1,431,119	$	6.43	5.44	828,589	$	6.36
$	6.86	-	7.26	985,648	$	7.08	4.05	985,648	$	7.08
$	7.40	-	7.88	726,606	$	7.61	7.69	398,243	$	7.63
$	8.06			157,210	$	8.06	7.85	78,604	$	8.06
$	8.09			82,160	$	8.09	5.83	82,160	$	8.09
$	8.30			565,893	$	8.30	7.26	85,696	$	8.30
				8,590,675	$	6.07	5.39	5,499,074	$	5.86

Summary of stock-based compensation expense by line item

	Year Ended March 31,
	2022		2021		2020
	(In thousands)
Cost of revenues	$	248	$	346	$	257
Research and development		1,676		1,509		1,487
Selling, general and administrative		1,069		999		822
Total	$	2,993	$	2,854	$	2,566

Schedule of weighted average assumptions

	Year Ended March 31,
	2022				2021				2020
Stock Option Plans:
Risk-free interest rate	0.66	-	1.62	%	0.22	-	0.42	%	1.35	-	2.30	%
Expected life (in years)			5.00				5.00				5.00
Volatility	47.7	-	49.1	%	41.9	-	47.6	%	36.5	-	39.7	%
Dividend yield			—	%			—	%			—	%
Employee Stock Purchase Plan:
Risk-free interest rate	0.04	-	0.07	%	0.12	-	0.15	%	1.58	-	2.43	%
Expected life (in years)			0.50				0.50				0.50
Volatility	45.6	-	57.4	%	67.1	-	68.6	%	33.5	-	43.1	%
Dividend yield			—	%			—	%			—	%