In 2005, financial analyst William Ng was tasked with kicking off Deutsche Bank's American Depositary Receipt business in the Chinese mainland, Hong Kong and Taiwan.

"At the beginning, it was pretty much a one-man shop," recalls Ng of his efforts to build the bank's market for ADRs, which are equity instruments that make it easier for non-US companies to list in the United States.

Ng says while he was "running around on the front line", his support staff consisted of only half the work hours of one other worker.

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China is now one of the most important areas for Deutsche Bank's ADR business and the region with the strongest growth momentum thanks to China's Internet boom, according to Ng, now Deutsche Bank's director and head of sales for global equity services in Greater China.

The technology, media and telecom sector accounts for more than 90 percent of Deutsche Bank's ADR client base in China. The bank doesn't disclose details on its Chinese clients, but they include a string of big names, such as the NASDAQ-listed JD.com, China's second-largest e-commerce company, and YY Inc, a leading Chinese live video-streaming platform.

But so much money is changing hands amid China's tech boom that it has attracted lots of attention from top global banks, leading to stiff competition.

ADRs were created by JP Morgan for British luxury department store Selfridges in 1927. As a depositary bank, Deutsche Bank acts as a fiduciary agent for both the issuer and the investor, Ng explains. The company deposits its common shares in the bank and the bank creates and issues the ADR, which can represent a fraction of a share or multiple shares.

It is a repackaging of a company's shares that makes it easier for both a foreign company to enter the US capital market and the US investor to buy shares in a non-US company.

TMT is by far the leading sector for Chinese companies to list in the US and the sector's dominance is expected to grow, Ng says.