11. STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Mar. 31, 2020

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, 2017	5,464,185	7,622,830		$	5.09
Granted	(1,029,684)	1,029,684		$	7.28
Exercised	—	(678,897)		$	4.22	$	2,460,812
Forfeited	9,800	(99,350)		$	5.06
Balance at March 31, 2018	4,444,301	7,874,267		$	5.45
Granted	(1,097,893)	1,097,893		$	6.74
Exercised	—	(823,456)		$	4.00	$	2,782,691
Forfeited	80,140	(131,675)		$	5.60
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	5.47	$	6.17
Options vested and exercisable		5,138,027	3.90	$	5.68	$	4,830,618
Options vested and expected to vest		8,056,574	5.44	$	6.16	$	5,581,363

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	910,273	$	4.07	4.08	910,273	$	4.07
$	4.90	-	4.99	1,336,396	$	4.97	5.15	897,047	$	4.96
$	5.13	-	5.59	926,921	$	5.32	4.39	891,696	$	5.32
$	5.69	-	6.16	825,827	$	5.92	4.45	644,888	$	5.90
$	6.24	-	6.70	1,399,575	$	6.58	5.11	784,655	$	6.49
$	6.82	-	7.26	1,296,755	$	7.05	5.30	721,208	$	6.93
$	7.40	-	8.06	628,211	$	7.77	8.99	136,376	$	7.59
$	8.09			85,360	$	8.09	7.69	43,304	$	8.09
$	8.30			617,893	$	8.30	9.33	-	$	-
$	9.20			108,580	$	9.20	0.84	108,580	$	9.20
				8,135,791	$	6.17	5.47	5,138,027	$	5.68

Summary of stock-based compensation expense by line item

	Year Ended March 31,
	2020		2019		2018
	(In thousands)
Cost of revenues	$	257	$	234	$	259
Research and development		1,487		1,310		1,141
Selling, general and administrative		822		722		670
Total	$	2,566	$	2,266	$	2,070

Schedule of weighted average assumptions

	Year Ended March 31,
	2020				2019				2018
Stock Option Plans:
Risk-free interest rate	1.35	-	2.30	%	2.53	-	2.91	%	1.84	-	2.49	%
Expected life (in years)			5.00				5.00				5.00
Volatility	36.5	-	39.7	%	35.6	-	37.3	%	35.5	-	36.5	%
Dividend yield			—	%			—	%			—	%
Employee Stock Purchase Plan:
Risk-free interest rate	1.58	-	2.43	%	2.09	-	2.50	%	1.04	-	1.42	%
Expected life (in years)			0.50				0.50				0.50
Volatility	33.5	-	43.1	%	32.6	-	37.7	%	38.8	-	51.1	%
Dividend yield			—	%			—	%			—	%