Many high-growth tech stocks doubled in value in 2020. That's not normal. It usually takes a bit more time for a stock to rise that much, even for an especially fast-growing business with an in-demand product or service. 2021 has been a different story. Many of these outperforming stocks of 2020 have taken a breather, some of them even declining by double-digit percentages.

Nevertheless, that doesn't mean growth investing is dead. On the contrary, many of them still offer compelling reasons to invest today. Three that could double over the next four years or so are Skyworks Solutions (SWKS -1.03%), Micron Technology (MU -0.76%), and T-Mobile US (TMUS 0.48%). Here's how three contributors think it could play out. 

A city skyline. An illustrated bubble with the characters "5G" in it are displayed above.

Image source: Getty Images.

An ever expanding need for high-quality mobile connectivity

Nicholas Rossolillo (Skyworks Solutions): The last couple of years have been busy ones for mobile connectivity chip designer Skyworks Solutions. The initial 5G mobile network rollout from telecoms translated into booming sales of new smartphones with a 5G connection-enabling chip in them. Sales at Skyworks are fast on the rise as a result, up 41% over the last two-year stretch -- impressive considering sales briefly hit the skids last spring.  

5G phones will no doubt continue to provide some upward momentum for Skyworks in the next three years as more of the next-gen mobile network becomes available to the masses. But Skyworks is much more than a smartphone component supplier. It also plays a hand in the design of infrastructure equipment used to build telecommunications systems, as well as the design of other devices that contain connectivity semiconductors: things like smart home devices, audio equipment, internet modems and routers, fitness equipment, and security systems.

The market for chips for products outside of smartphones -- which Skyworks calls its "broad markets" business -- has been steadily growing for years and makes up about one-third of revenue. But it will get a big boost in this department from the acquisition of Silicon Laboratories' (SLAB -1.54%) automotive and network infrastructure segment. The acquisition will add about $400 million a year in sales at the most recent annualized run rate and yield Skyworks exposure to some massive new markets, specifically the growing connected and electric auto movement.

With its own core business still growing at a fast double-digit percentage clip, adding a new breed of chip designs into the mix should help Skyworks sustain its momentum. Granted, as is the case with semiconductor stocks, I don't expect this advance to move up in a straight line. Chip industry sales are cyclical and can ebb and flow from year to year. But over the next few years, 5G will continue to proliferate and dozens of more technologically advanced vehicle models will hit the road. I see plenty of room for this chip company to grow -- it could be double the size it is now in another four years' time.

Micron shares trade at an oversize discount today

Anders Bylund (Micron Technology): Memory chip maker Micron Technology has seen some hard times lately. Let me clarify that. Micron's stock is in dire straits at the moment. The business is as healthy as ever.

Micron generated $2.4 billion of free cash flow and $12.6 billion in earnings before interest, taxes, depreciation, and amortization (EBITDA) over the last four quarters. These generous profits were generated from $27.7 billion of top-line revenue. All of these important metrics have surged higher in the last two years:

MU Revenue (TTM) Chart

MU Revenue (TTM) data by YCharts

Micron set many operating records in the recently completed fiscal year 2021. Mobile memory sales reached new highs. Automotive and industrial memory chips also topped their old record sales by significant margins. Even the consumer-facing business landed record sales this year.

All of these records were achieved in the midst of a sector-wide manufacturing crisis. Micron runs its own chip-making plants, which helps the company dodge the logjam in the leading contract manufacturing specialists' production pipelines. Production technology upgrades are generally on time and within Micron's generous infrastructure budgets.

So Micron's operations are humming right along while most of the semiconductor industry suffers production-level restrictions. Market makers must be impressed, right?

Well, no. Micron's stock has retreated nearly 30% from April's multi-year highs and trades at a mere 7.9 times forward earnings. In other words, Micron's shares are hanging out in Wall Street's bargain bin despite the company's impressive business results. The company will set the record straight over time, and I will be amazed if share prices haven't at least doubled from this rock-bottom level in the next three years.

This 5G leader should have little trouble doubling in the years ahead

Billy Duberstein (T-Mobile): When you think of large telecom stocks, you don't normally think of big-time gains. Yet that's exactly what investors should see if T-Mobile hits its long-term financial targets as a result of its leadership in 5G.

T-Mobile's stock has fallen recently following an unfortunate data breach, and the stock is currently down about 16.5% from recent highs. But as the news around the data breach falls further into the past, it sets T-Mobile stock up to potentially double in the next four years.

In fact, it wouldn't even take a herculean effort for the stock to double by 2025. At its March analyst day, management raised its long-term forecasts, having grown even more bullish on both revenue and cost synergies stemming from the 2020 acquisition of Sprint.

That integration takes some upfront investment, so T-Mobile's profits and free cash flow are muted at the moment; however, management now sees $13 billion to $14 billion in free cash flow by 2023 to 2024 and over $18 billion in free cash flow by 2026.

Assuming $18 billion in free cash flow -- the low end of T-Mobile's target -- and just a 15 P/E ratio in 2025, one could see T-Mobile trading at a market cap of $270 billion, up about 75% from today's share price. However, T-Mobile also plans to return $60 billion to shareholders in the form of share repurchases by 2025. That's nearly 40% of T-Mobile's market capitalization today.

Of course, T-Mobile's share price will likely go up as repurchases are made and the share count declines; however, even if T-Mobile retires only 20% of its shares outstanding, compounded with a 75% increase in market cap, its share price would appreciate about 118%.

Skeptics would point out that T-Mobile's rivals Verizon Communications and AT&T have forward P/E ratios of just 10 and 8.5, respectively. However, those bargain-basement valuations could reflect the fact that T-Mobile has taken the lead in 5G capabilities and appears set to gain market share from each in the years ahead. Both Verizon and AT&T also pay out dividends instead of repurchasing stock, and both companies also have more sizable debt loads by comparison.

With the overall market's forward P/E multiple around 21.5 today, it's not unreasonable to use 15 for an industry leader like T-Mobile. And given that T-Mobile has a history of beating its own forecasts, a doubling in its share price by 2025 is not only possible, but, I think, likely.